The un-whipped Lemon Ganache must chill in the fridge for at least 6 hours, preferably overnight, before you whip it up into a fluffy yellow cloud. So plan accordingly.
 

Lemon Curd with Gelatin
 

• Bakers Note; Make the lemon ganache right away after preparing the lemon curd to ensure the gelatin doesn't set too much, which would make it hard to combine smoothly with the ganache.
   
• If using gelatin leaves: Soak 3 gelatin leaves in very cold water for at least 10 minutes before starting the lemon curd. After 10 minutes, squeeze out the excess water from the gelatin leaves before adding them to the warm lemon curd.
   
• If using gelatin powder: In a small bowl, combine 2 1/2 teaspoons of gelatin powder with 40 grams of cold water. Stir until the gelatin dissolves, then set aside.
   
• For the lemon curd: In a medium-sized measuring cup, add 90 grams powdered sugar, 17 grams cornstarch, 2 large whole eggs, 1 egg yolk, and 125 grams freshly squeezed lemon juice. Whisk these ingredients together with an immersion blender until you have a homogeneous mixture.
   
• Transfer the mixture to a medium-sized saucepan. Cook over medium-low heat, constantly stirring with a whisk or spatula, and make sure to scrape the sides of the pan. Continue until the mixture thickens to the consistency of a soft pudding, which should take about 5 minutes.
   
• Remove the saucepan from the heat. Immediately whisk in either the gelatin mixture or the drained gelatin leaves, stirring until fully melted and incorporated. After the gelatin leaves have fully dissolved into the warm lemon curd, add 75 grams of lukewarm heavy cream, about 30°C/86°F. Stir the mixture well to ensure it remains smooth and consistent. Using lukewarm cream is key to maintaining the right temperature balance, preventing the gelatin from setting too quickly while preparing for the next steps in making your ganache
   
• Proceed immediately to preparing the lemon ganache. It's important to work swiftly.
   

Whipped Lemon Ganache
 

• Bakers Note; For this ganache to work, make sure to use premium-quality white chocolate containing cocoa butter, such as Callebaut velvet 32%. The type of white chocolate is important in this recipe.  
   
• Coarsely chop 300 grams of high-quality white chocolate that contains cocoa butter. A serrated knife works best for this. Place the chopped chocolate into a heat-proof bowl or measuring jar.
   
• In a medium saucepan, bring 500 grams of heavy cream to a simmer with 1 teaspoon of vanilla bean paste (or if you're feeling extra fancy and using a vanilla bean, using a sharp knife, carefully split one vanilla bean lengthwise and add it into the saucepan) and a pinch of sea salt, heating it to about 80°C/176°F. If you used a vanilla bean, remove the vanilla bean pod from the saucepan. It's important to scrape and squeeze as much of the flavorful gooey vanilla seeds back into the cream as possible to ensure the ultimate flavor.
   
• Pour the hot cream over the chopped white chocolate. Let it sit for 1-2 minutes, then stir slowly with a spatula until the mixture is smooth and the chocolate is completely melted.
   
• Incorporate the 400 grams of lemon curd immediately into the warm chocolate and cream mixture. If available, use an immersion blender to emulsify until smooth. When done the lemon ganache will thicken slightly.
   
• Transfer the warm ganache to a clean container. Cover with plastic wrap, pressing it directly against the surface to avoid skin formation. Chill in the refrigerator, ideally overnight.
   
• Remove the chilled ganache from the fridge, remove the parchment paper. The ganache will be firm at this stage.
   
• Transfer the firm ganache to the bowl of a stand mixer with a whisk attachment. Whip on high speed for 30 up to 90 seconds beginning to check the consistency after about 30 seconds, then continue to check every 10 seconds. Once the ganache starts to show whisk marks and reaches a light, airy, mousse-like consistency it is done!
   
• Store any unused whipped lemon ganache in an airtight container covered with plastic wrap, pressing it directly against the surface, place in the refrigerator It should remain light and fluffy, similar to a mousse, and can last 3 to 5 days. If needed re-whip lightly to bring it back to a fluffy consistency.

White Chocolate & Sponge Cake
 

• Baker Note; “When preheating the oven for my cakes, always use the ‘top and bottom heat’ setting. Please avoid using the fan-forced option, unless otherwise specified.”
   
• Twenty minutes or longer before baking, Set your oven rack in the center of the oven, And preheat the oven to 170C°/ 338F°.  
   
• Grease your wire racks lightly with butter and set them aside; this will prevent the cake from sticking to the wire rack.
   
• Use a small piece of cold butter, and gently rub the cold butter over the bottom and the sides of two 20 cm ( 8-inches) round baking pans. This technique of using a small piece of cold butter ensures an even, ultra-thin coating. Place a circle of parchment in the bottom of the pan. Add a tablespoon of all-purpose flour and tap it around the inside of the pan until all the buttered surface is covered 100%, then turn the pan upside down over a sink and tap out the excess flour. If you don’t have two pans, it’s okay to bake the cakes in stages; The cake batter will be kept at room temperature until needed.
   
• Prepare your finely grated white chocolate;  Use the grating attachment on your mixer for this step; Collect the grated chocolate directly into a ziplock bag and place the grated chocolate/ziplock bag in the fridge until needed. I recommend you weigh the chocolate after you have grated the chocolate.
   
•  Bakers note; If you don't have such an attachment on your mixer, use a Microplane or a hand grater. To grate chocolate by hand, make sure that it is cold, or it will melt. I recommend you collect the grated chocolate immediately into a zip-lock bag. Place the grated chocolate in the fridge to get cold.
   
• Bakers note: An egg's white-to-yolk ratio can vary. It’s therefore advisable to weigh the egg yolks and egg whites and add or reduce them if needed.
   
• Combine 110-gram all-purpose flour or pastry flour, 50-gram potato starch ( or 50-gram all-purpose flour), and 1 teaspoon baking powder in a medium bowl. To get the cake layers you truly deserve, sift the flour mixture a few times to get the flour as aerated and light as possible.
   
• Bakers note; Wipe your mixer bowl with a paper towel dampened with a little lemon juice to eliminate any trace of grease so that the meringue whips up well.
   
• In a clean bowl of a stand mixer fitted with the whisk attachment, put 210 grams of egg whites and a pinch of cream of tartar; whip the meringue on medium speed until it is climbing to the top of the bowl and the meringue is white, glossy, and holds a soft, floppy peak. About 3 minutes. Use a timer!
   
• As soon as the meringue is glossy, add one tablespoon at a time of 200 grams of superfine sugar, and mix on medium-high speed for 3 minutes more to make a very shiny and thick meringue (Use a timer!)
   
• As soon as all of the sugar is incorporated and the meringue is thick, with your mixer on medium speed, add the 140 grams of egg yolks (all at once) and whip for 7 seconds and no longer, or your cake will become flat and dense. Stop the mixer and remove the bowl from the mixer.
   
• Bakers Note; Instead of using a large spatula for maximum volume, use a balloon whisk to fold the flour mixture into the cake batter. A spatula will deflate the cake batter more.
   
• Sift one-third of the flour/potato starch mixture over the whipped meringue/yolk mixture and gently combine with a balloon whisk until well incorporated; repeat this step twice. Use a large silicone spatula at the end of the folding to scrape the side and the bottom of the mixer bowl to make sure all the flour is integrated. Set aside for now while you warm the cream.
   
• In a small saucepan, warm 60-gram heavy cream and 1 teaspoon vanilla bean paste over medium heat until warm ( about 60 seconds, about 50C°/122F° ), then quickly pour the warm cream around the edge of the bowl and gently combine with a balloon whisk or spatula without deflating the batter too much. Leave the cake batter to rest on the kitchen counter for 2 full minutes.
   
• Carefully fold in the 100-gram grated white chocolate in the cake batter in two additions until evenly incorporated. Make sure to check the bottom of the bowl as well, if the grated chocolate is not well incorporated in the cake batter the cake will bake unevenly. 
   
• Use a scale to weigh the cake batter, then divide the cake batter between the two prepared pans—about 420 grams in each pan. 
   
• Give your pans just a really good spin on the table, what that does is it takes the cake batter up the side of the pan a little bit, just so that as it's baking, it already has an attachment to kind of move up the side of the pan. So, don't be afraid to really give it a good spin. Get that batter moving up. Don’t tap your baking pans on the kitchen counter to try to get things to level out, especially with this style of cake batter, because banging your pans or dropping it on the table to level the batter actually gets rid of all the air bubbles that you just incorporated into the batter. 
   
• Bakers Note; Using an oven thermometer will ensure even baking results each time, as every oven is different. Always go with the reading on your oven thermometer rather than the temperature you set on your oven.
   
• Bake both cakes until golden brown, and firm on top and the cake springs back when pressed lightly in the center, about 18 to 20 minutes, depending on your oven and baking pan. Mine was done at 20 minutes. To check if the sponge cake is ready after 18 minutes of baking, you should first look through the oven window rather than open the oven door. If the center appears slightly sunken, give it a minute or two longer while keeping an eye on it. At the 20-minute mark, if the center seems almost set, carefully open the oven and gently press the top of the cake. It should feel firm to the touch and may have a slight bounce to it. This method allows you to monitor the cake's progress without disrupting the baking process.
   
• Then immediately, without delay, run a knife between the sides of the pan and the cake, and invert the cakes immediately onto a wire rack; remove the parchment paper and leave it to cool completely on a wire rack. 
   
• Cover the cake layers with plastic wrap or in a large ziplock bag to prevent them from drying out until you are ready to use them.
   
• Split each one in half to make a four-layer cake. 
   
• This white chocolate sponge cake is super delicious on its own and even more so when paired with a cream-based filling, which adds extra moisture to the cake. I highly recommend filling it with a lemon flavor or any fruit flavor of your choice; the tartness or sweetness of the fruit complements the rich vanilla and white chocolate beautifully.

Blueberry Jam

• In a medium saucepan, add 250 grams of frozen blueberries, 2 teaspoons of white sugar, 1 tablespoon cornstarch, and 35 grams of freshly squeezed lemon juice.
   
• Warm over medium -low heat to soften the blueberries and bring the mix to a boil. Stir often to prevent burning at the bottom.
   
• Continue boiling for two minutes more. Then place the blueberry jam in the fridge to cool and thicken up. it's key to ensure it is cold and has a thick consistency with minimal juice.
   

Blackberry Jam

• In a medium saucepan, add 250 grams of frozen blackberries, 2 teaspoons of white sugar, and 35 grams of freshly squeezed lemon juice.
   
• Warm over medium -low heat to soften the blaclberries and bring the mix to a boil. Stir often to prevent burning at the bottom.
   
• Continue boiling for two minutes more. Then place the blueberry jam in the fridge to cool and thicken up. it's key to ensure it is cold and has a thick consistency with minimal juice.
   

Greek Yogurt & Frosting 
 

• Bakers Note: Use only heavy cream (or heavy whipping cream) with a 40% fat content. This higher fat content is key for whipping up this Greek Yogurt Cream  that's both thick and stable, providing the perfect base for your frosting.
   
•  Make sure to use full-fat, natural Greek-style yogurt with a 10% fat content. Your Greek Yogurt should be notably thick. If you find the yogurt too watery, a simple fix involves straining it through a fine-mesh sieve over a bowl, covered with plastic wrap, and left to drain in the fridge for a few hours or, ideally, overnight. This step is crucial to ensure your Frosting achieves the perfect consistency, avoiding a watery outcome that could compromise your frosting's structure.
   
• In a stand mixer fitted with the whisk attachment, beat together 50-gram powdered sugar, 150-gram cold Greek yogurt, 150-gram cold heavy cream, one teaspoon of vanilla bean paste. Mix on medium-high speed until light, fluffy and thick. It takes about 1-3 minutes. Whipped yogurt frosting destabilizes (softens) when overmixed, so keep an eye on the frosting as soon as it thickens.
   
• Stop the mixer and scrape down the sides and bottom of the bowl. Then, remove the bowl from the mixer.  Store in an airtight container until needed. If needed re-whip lightly before use.

Lemon Syrup

• In a small saucepan over low heat, stir the 50 grams of freshly pressed lemon juice and 25 grams of white sugar together until the sugar has dissolved. (The longer the syrup simmers, the more it will reduce and thicken.) For a syrup that really soaks into a cake, keep it reasonably runny. About 3 minutes. Cool down to roomtemp before using.

To Assemble

• Get all the components for the cake ready. Before adding the blackberry and blueberry jam to the cake, it's key to ensure it is cold and has a thick consistency with minimal juice. If yours is on the juicier side, don't hesitate to strain off the excess liquid—this helps prevent the sponge from becoming too moist. You’ll likely have some compote left over; it's wonderful on bread or with yogurt. Store any extra in the fridge in an airtight container for up to five days.
   
•  Place the first cake layer on a cake stand that fits in your fridge and drizzle the first cake layer with a little lemon syrup, concentrating most of it around the edge, the berries will help moisten the middle.
   
• Remove the whipped lemon ganache from the fridge, if needed re-whip before use. Fit a pastry bag with a large tip and fill it with one-third of the whipped lemon ganache.
   
• Pipe the lemon ganache onto the cake in a spiral motion, creating a series of concentric circles starting from the outer edge and moving towards the center. Leave sufficient space between each circle for the jam. After piping the ganache, fill all the empty spaces within the spirals with 2 to 3 spoons of cold blackberry jam.
   
• Arrange the second cake layer on top and press down lightly to seal and secure.
   
• Remove the cold Greek yogurt from the fridge, if needed re-whip lightly. Fill a piping bag with Greek yogurt frosting, attaching a large round nozzle.
   
• Pipe the frosting onto the cake in a spiral motion, creating a series of concentric circles beginning at the outer edge and working your way toward the center. Be sure to leave enough space between each circle. Once you have finished piping, spoon a few tablespoons of blackberry jam or blackberry jam into the spaces between the piped frosting, filling them completely. Place the third cake on top, ensuring it is centered. Gently press down to secure it in place.
   
• Transfer another one-third of the whipped lemon ganache into a piping bag fitted with a large round nozzle. Store the remaining lemon ganache in an airtight container in the fridge. Use it to create a chic, semi-naked look around the cake before serving.
   
• Carefully pipe the ganache in a spiral pattern on the third cake layer, forming concentric circles from the outer edge inward, ensuring to leave deliberate spaces between each for the jam.
   
• Spoon a few tablespoons of cold blueberry jam into these gaps, generously covering the cake's surface to infuse it with rich flavor and to provide a beautiful contrast with the ganache's delicate color.
   
• If there’s any Greek yogurt frosting remaining, dollop it over the jam-filled spirals, then delicately place the fourth cake layer on top. Apply light pressure to adhere it properly.
   
• Wrap the cake in plastic wrap and let it rest in the refrigerator overnight. This will not only allow the flavors to meld and intensify but will also give the layers time to set, ensuring each slice is delicious moist.
   
• When you're ready to serve, gently remove the cake from the refrigerator and discard the plastic wrap.
   
• Take the reserved whipped lemon ganache out of the fridge, give it a quick whip to bring back its light texture, and add a few spoonfuls on the top layer.
   
• Smoothly spread the lemon ganache in a thin layer over the top and around the sides using a spatula to create a chic, semi-naked look.
   
• Your cake is now ready to be enjoyed.