Sponge Cake Layer

• Twenty minutes or longer before baking, set an oven rack in the bottom third of the oven and preheat the oven to 165C°/ 325F°. 
   
• Line a 23 cm ( 9 inches) springform with parchment paper and set it aside. Make sure your springform has a tight seal so that the batter won't leak out. I always cover the bottom and side of my springform with aluminum foil and set my springform on a baking sheet in case anything escapes the seam.
   
• In a medium bowl, sift together the 45-gram all-purpose flour, 45-gram potato starch, and 1/2 teaspoon baking powder and set aside for now.
   
•  Wipe the inside of stainless steel or a glass bowl and the whisk attachment with a paper towel moistened with a little lemon juice to make it perfectly clean, This step is done to eliminate any trace of grease, which would hinder the egg whites from stiffening.
   
• Whip the 115 gram egg whites on high speed until foamy, about 30 seconds, to make sure that the eggs are free from fat and are going to create foam.
   
• Then add 1/8 teaspoon cream of tartar, this will increase the strength of the proteins, turn the mixer to medium speed until you get a medium peak, about 3 minutes.
   
• Then turn the mixer to low speed, and slowly add the 125-gram superfine sugar to the whites, a tablespoon at a time so it doesn't crush the foam you build up.
   
• Once all of the sugar has been added, turn the mixer to medium-high speed and whip to a medium-stiff peak, about 3 to 5 minutes.
   
• Remove the bowl from the mixer.
   
• Combine the 55-gram egg yolks, and 1 teaspoon vanilla bean paste in a small bowl, give it a quick whisk and gently fold it together with the whipped meringue using a balloon whisk until just combined ( you will be able to see a few streams of egg yolks)
   
• Sift the flour/starch mixture onto the egg/meringue mixture in two increments. For maximum volume, use a balloon whisk or your whisk attachment and gently fold the flour mixture into the batter until fully incorporated. Sift the flour over the batter each time. Periodically shake out the batter that collects inside your whisk; use a large silicone spatula at the end of folding in order to reach the bottom of the bowl.
   
• Add the warm heavy cream to the side of the bowl and gently combine with a spatula.
   
• Scrape the batter into the prepared spring form.
   
• Bake in the bottom third of the oven at  165C°/ 325F° until the cake layers are golden brown and spring back when gently touched with your fingertip and a toothpick inserted into the center of each cake comes out clean, about 23 to 25  minutes.
   
• Avoid opening the oven door before the minimum baking time has elapsed because this fragile cake could fall. Test toward the end of baking by opening the oven door a crack, and if the cake doesn’t appear done, continue baking for some minutes more.
   
• To prevent the collapse of the delicate foam structure, the cake must be unmolded as it is baked; while still hot, run a knife or metal spatula between the sides of the pan and the cake, and invert the cakes onto a prepared wire rack, leaving the parchment in place. If they steam in the baking pan, they will toughen. 
   
• Clean your 23 cm ( 9-inches) springform, place a new piece of parchment paper in the bottom, place the cooled cake layer bottom-up in the springform, and wrap the collar/acetate sheet around the inside of the pan. The acetate sheet is used to extend the height of the sides of the pan. Acetate is a thick, shiny strip of plastic, also known as acetate cake collar. Or cut a long strip of parchment paper, 71 cm ( 28 inches) in length. Use a touch of baking spray or butter to lightly grease the back of the collar/acetate to help it stick to the pan and stay in place.  
   
• Set aside while you make prepare the vanilla ice cream

Directions for the vanilla bean ice cream
 

• Place the egg yolks in the bowl of a stand mixer fitted with the whisk attachment.
   
•  Split the vanilla beans lengthwise, and use the tip of a sharp knife to scrape out the seeds; add the vanilla seeds to the bowl with the egg yolks.
   
• Mix the egg yolks and vanilla bean seeds at medium-high speed for 8 minutes.
   
• In the meantime, In a medium saucepan add the sugar, glucose, and water (without stirring). Set over medium heat and clip a candy thermometer onto the side,  bring to a boil and simmer until an instant-read thermometer registers  112C/233F°.
   
• Then immediately remove it from the heat. Let the bubbles calm down for a couple of seconds.
   
• Then, slowly pour the hot sugar syrup into the yolks while mixing on low speed. Avoid hitting the whisk with the syrup; instead, aim for the gap in between the side of the bowl and the whisk.
   
• Once all the syrup has been added, increase the mixer speed to medium-high and whip until the bowl is cool to the touch, about 10 minutes. The egg yolks will initially look watery with the syrup addition, then lighten in color and thickens as the two are beaten together.
   
• Stop the mixer and scrape the side and the bottom of the bowl; add the 250-gram mascarpone, then whip on low speed until smooth and combined. About 1 minute.
   
•  Remove the bowl from the mixer and set it aside for now.
   
• In the bowl of a stand mixer fitted with the whisk attachment or in a large bowl and using an electric beater, whip the cream on medium speed until just thick, about 2-3 minutes.
   
• Fold the whipped cream into the egg yolk /mascarpone mixture. This takes several turns of your rubber spatula; combine slowly as you don't want to deflate all the air in the whipped cream.
   
• Pour the vanilla ice cream on top of the sponge cake, and use a silicone spatula to smooth down the top.
   
• Cover the springform tightly with double plastic wrap or aluminum foil and place in the freezer for at least 6 to 8 hours, I freeze mine overnight.
  
   

Raspberry Sorbet Layer
 

• Combine the frozen raspberries, the cold sweet condensed milk, lemon zest, citric acid ( optional) glucose, and fresh lemon juice in a food processor and process until smooth and creamy. about 3-4 minutes. In the beginning, it seems like it never turns into a sorbet, but just keep going and you will get end up with this beautiful and delicious raspberry sorbet.
   
• Remove the ice cream cake from the freezer, and top the frozen vanilla ice cream layer with the raspberry sorbet, use a spatula, and quickly spread, an even layer on top of the vanilla ice cream layer.
   
• Cover with plastic wrap or aluminum foil and return it immediately to the freezer and freeze for at least 3 to 4 hours or until firm.
   
• Without the meringue topping this ice cream cake can be made ahead, well covered holds up wonderfully in the freezer for up to 4 weeks.

Directions for the Marshmallow frosting
 

• This batch will modestly frost this ice cream cake, but if you like a loftier frosted look with lots of fluffy swirls. make 1 1/2 batches.
   
• Pour about 4 cm ( 2- inches ) of water into a medium saucepan and place over medium heat.
   
• Wipe your mixer bowl, your whisk of an electric mixer, and your hand whisks with a paper towel dampened with a little lemon juice to eliminate any trace of grease.
   
• Place your egg whites, sugar, water (→the water makes the whipped meringue light and airy and helps to thin out the egg white protein), glucose (or light corn syrup), cream of tartar ( or fresh lemon juice) into a heatproof metal or glass bowl, Whisk the ingredient together to make a thick slurry.
   
• Place the metal/glass bowl over the pan of simmering water ( make sure the pot is small enough that the bowl sits above the water and not directly touching it, or you may end up with scrambled egg whites.
   
•  Whisk occasionally until the mixture is very hot to the touch, and has the color of milk, and the sugar is completely dissolved. The mixture should not feel grainy when rubbed between your fingers
   
• Scrape the sugar -egg white mixture into a stand mixer fitted with a whisk attachment. ( be careful the mixture is hot) 
   
• Whip on medium speed for 4 to 5 minutes or until the mixture has tripled in volume and is thick and glossy and looks like shaving cream.
   
• Add vanilla bean paste or pure vanilla extract, and whip on low speed until just combined. 
   
• Make sure to not over-whip the marshmallow frosting, it can get pretty thick and stiff if you overmix it and make it difficult to decorate your ice cream cake.
   
• Use immediately.

• Remove the ice cream cake from the freezer 5 minutes before serving, remove plastic wrap and remove the ice cream cake from the rim of the springform pan, remove the acetate sheet, and place the cake onto a serving plate or cake stand.
   
• Immediately spread the marshmallow frosting all over the ice cream, using a metal spatula or the back of a spoon to create swirls. Using a kitchen torch blowtorch, lightly brown the marshmallow frosting, and make sure to keep the torch moving so it doesn't burn the meringue.
   
• For maximum freshness and deliciousness, serve immediately. Use a sharp knife ( a serrated knife is best) to cut your ice cream cake. Store leftovers in the freezer for up to 3 days.
   
• The ice cream cake can be assembled 3 days ahead. Keep frozen but don't cover the cake, the meringue won't freeze hard and you'll ruin the pretty swirls/design. Bring the ice cream cake to room temperature about 5 minutes before serving.