Fluffy Vanilla Sponge Cake
 

• 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 an oven rack in the center of the oven, and preheat the oven to 170C°/ 338F°. 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.
   
• Grease your wire racks lightly with butter and set them aside; this step 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 three 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 three pans, it’s okay to bake the cakes in stages; The cake batter will be kept at room temperature until needed.
   
• Bakers note: The egg white to yolk ratio in an egg can vary to such a degree. Therefore, weighing the egg yolks and egg whites as mentioned in the recipe and adding or reducing them if needed is advisable. Place 7 large eggs in lukewarm water for a few minutes.
   
• Bakers Note: All-purpose flour with 8-9% gluten is ideal for tender sponge cake layers; I use 9%. While 10% works, less gluten is preferable. Enhance tenderness by mixing in potato starch which is labeled as potato flour in Scandinavia.
   
• In a medium bowl, sift together 90 grams of all-purpose flour or pastry flour, 90 grams of potato starch, and one teaspoon of baking powder. To get the cake you truly deserve, sift the flour mixture twice to make the flour as aerated and light as possible.
   
• For the yolk mixture, in the bowl of a stand mixer fitted with the whisk attachment, whip 50 grams of superfine sugar, 140 grams of egg yolks, and two teaspoons of vanilla bean paste on medium speed until pale yellow, tripling its volume, and all of the sugar is dissolved—about 5 to 8 minutes. Set aside for now.
   
• Wipe a stainless steel bowl and the whisk of an electric mixer with a paper towel dampened with a little lemon juice to eliminate any trace of grease.
   
• Put 210 gram egg whites and a pinch of cream of tartar into the bowl. Using the whisk attachment, whip on medium high speed for about 3 minutes until the whites are glossy white. Add the sugar ( 200 grams) one tablespoon at a time over 3 minutes to make a very shiny and stiff meringue. Remove the bowl from the mixer.
   
• As soon as the meringue is done, place the whipped meringue into a large bowl, add the whipped egg yolk mixture on top, and carefully fold them together using a balloon whisk rather than a spatula. You don't want to deflate the mixture, so try to do as little folding as possible.
   
• Sift the flour/starch mixture onto the egg mixture in two increments. For maximum volume, use a balloon whisk or a large silicone spatula, and gently yet confidently fold the flour into the batter with strength! It’s better to make a few powerful folds than 15 half-hearted ones. If you don’t get it mixed in just right, you might end up with a sponge cake that’s all heavy at the bottom and too fluffy at the top. You’ll know you’ve done it right when the batter gets a bit less puffy and looks more uniform.
   
•  Use a large silicone spatula at the end of the folding to reach the bottom of the bowl and scrape the batter into the pan(s).
   
• Evenly distribute the batter among the three prepared pans, about 250 grams in each baking pan. Use your offset spatula to spread it into an even layer.
   
• Bakers Note: Give your pans just a really good spin on the table, what that does is it takes the 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. 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. 
   
• Bake both cakes until golden brown and the top of the cake feels firm and has a pale golden colour. about 15 to 17 minutes, depending on your oven and baking pan. Mine was done at 16 minutes. To check if the sponge cake is ready after 15 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. Then 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. Because this sponge cake is going to be filled  with a cream based filling, it doesn't matter if you overbake it for a minute longer, It's better to do that than end up with a sponge cake that is wet in the bottom.
   
• Immediately without delay run a knife or metal spatula between the sides of the pan and the cake, and invert the cakes onto a prepared wire rack, remove the parchment paper, and leave them to cool completely on a wire rack.
   
• Repeat with the final layer.
   
• If not used immediately, wrap them well in plastic to keep them from drying out.
   
• Each cake layer is about 4 cm high.

Lemon Syrup
 

• In a small saucepan over low heat stir 80-gram lemon juice and 50-gram sugar until the sugar has dissolved.
   
• For a syrup that really soaks into a cake, keeps it runny.

Strawberry Passion Fruit Yogurt Filling

• Squeeze out the inside of 6 passion fruits; you need 60 grams, both the seeds, juice, and pulp. Place the bowl with passion fruit puree in the fridge to get cold while you prepare the yogurt whip cream.
   
• Finely chop your 250 grams strawberries, and place them in the fridge as well to get cold while you prepare the yogurt filling.
   
• Bakers note; before you start with the whipped yogurt frosting, the colder the cream and the colder the Greek yogurt is, the easier and more successful it will whip and creates the lightest whipped yogurt frosting! for best results, take the cream and Greek yogurt out of the fridge and chill the cream and greek yogurt in the freezer for 15 minutes before you start. If you don't have a freezer just make sure your cream and Greek yogurt is really, really cold; a slightly warm cream does not whip up well.
   
• In a stand mixer fitted with the whisk attachment, beat together 50 grams of sifted powdered sugar, 300 gram of cold Greek yogurt, 300 gram of cold heavy cream; use a sharp knife to split the vanilla bean lengthwise and scrape out the seeds and add them into the mixing bowl, zest from 1 lemon.
   
•  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; remove the bowl from the mixer.
   
• Take the refrigerated cold passion fruit puree, and chopped strawberries out of the fridge, add them to the whipped yogurt frosting and combine lightly with a spatula. Set aside in the fridge.
  
  
  Assemble
  
   
• To assemble the cake layers, I highly recommend using a cake ring, as the cake can feel wobbly or unstable. The cake ring I use is 20 cm (8 inches) in diameter and has a height of 12 cm ( 5 inches). 
   
• To assemble the cake, Place a cake ring in the center of a cake stand or baking sheet lined with clean parchment paper (*make sure the cakestand or baking sheet fits in your fridge). Use a strip of acetate to line the inside of the cake ring. Another option is; Place a strip of acetate around the cake at the end and then place a cake ring around the cake.
   
• The secret to an ultra-moist cake is to brush the cake layers with a little lemon sugar syrup using a pastry brush, concentrating most of it around the edge. 
   
•  Scoop half the amount of the strawberry & passion fruit Yogurt Filling on top of the first cake layer with a spatula, spread it on top of the first cake layer.
   
• Place the second cake layer on top of the strawberry & passion fruit Yogurt Filling, and press down lightly to attach the cake. Scoop the remaining strawberry & passion fruit Yogurt Filling on top of the second cake layer with a spatula, spread it evenly on top.
   
• Wrap the cake in plastic wrap—place in the fridge for at least 6 hours.
   
• For the lemon glaze, in a medium bowl, combine 200 grams of powdered sugar, add 50 grams of lemon juice and juice from 1 blackberry or raspberry and mix until it forms a thick glaze. 
   
• Remove the cake from the refrigerator, remove the plastic wrap, and pour the pink lemon glaze on top of the third cake layer. Place back in the fridge until the icing is set.
   
•  Place the cake in the fridge overnight before slicing and serving. Cover the cake with a cake dome to keep it fresh.
   
• This cake is best to enjoy within 2 days.