Cake 'Summer Cloud' with Strawberry Mousse and White Chocolate

Preheat the oven to 170°C (top and bottom heat, no fan). Prepare a springform pan with a diameter of 22-24 cm. Line the bottom of the pan with parchment paper, securing it with the ring. Do not grease the sides – this way the sponge cake rises evenly along the walls and does not sink after baking.

In one bowl, combine all-purpose flour and potato starch. Sift them together through a sieve at least twice. This step is extremely important as it aerates the flour, which contributes to the fluffiness of the sponge cake and prevents lumps from forming.

Very carefully separate the egg whites from the yolks. Make sure that not a drop of yolk has gotten into the egg whites, as even a small amount of fat will prevent them from whipping into stiff peaks. Place the egg whites in a large, ideally clean and dry bowl (metal or glass). Add a pinch of salt and start beating with a mixer on medium speed. When the mixture becomes white and thick, increase the speed to maximum and continue beating until the mixture is stiff and glossy.

Without stopping the beating on the highest speed, add the fine sugar to the egg whites, one tablespoon at a time. Do this slowly, allowing each portion about 30 seconds to dissolve before adding the next. After adding all the sugar, continue beating for another 2-3 minutes until the mixture becomes very thick, glossy, and silky, and the sugar crystals are undetectable (rub a bit of the mixture between your fingers).

Reduce the mixer speed to the minimum. Add one egg yolk at a time, mixing only until the ingredients are combined, no longer than 10-15 seconds after each yolk. Finally, add the vanilla extract and mix briefly.

Set aside the mixer. Now you will use a spatula or a large wooden spoon. Gradually add the sifted flour to the egg mixture in 3-4 batches. After each addition of flour, very gently fold the mixture, making motions from the bottom of the bowl upwards (the so-called folding technique). Do this slowly and carefully to avoid deflating the air bubbles in the foam. Mix only until no dry flour is visible.

Immediately transfer the prepared mixture to the prepared springform pan. Smooth the surface with a spatula. Place in the preheated oven and bake for about 35-40 minutes. Towards the end of baking, check the cake with a wooden stick – if it comes out dry when inserted in the center, the sponge is ready. If there is raw batter on it, bake for another 5 minutes and check again.

After baking, immediately remove the springform pan from the oven. Drop it from a height of about 30-40 cm onto the countertop or floor. This will help the air bubbles disperse evenly and prevent the sponge from collapsing. Set aside to cool completely. Only when the sponge is cold, use a knife to separate it from the edges of the pan and remove it. Cut it in half with a long, serrated knife into 2 equal layers.

In a small saucepan, place the water and sugar. Heat over medium heat, stirring, until the sugar is completely dissolved. Remove from heat, add freshly squeezed lemon juice. If using mint, add a few leaves and set aside to cool completely. Before using, remove the mint leaves.

Pour the gelatin into a small bowl and add 60 ml of cold water. Mix and set aside for 10 minutes to swell. In the meantime, wash, dry, and remove the stems from 500 g of strawberries. Blend them into a smooth puree using a stand or hand blender.

Pour about 1/3 of the strawberry puree into a small saucepan and heat over low heat. Do not bring to a boil, it should just be hot. Remove from heat, add the softened gelatin, and whisk vigorously until completely dissolved. Combine with the rest of the cold puree and mix thoroughly. Set aside to cool slightly.

In the meantime, chop 50g of white chocolate and melt it in a water bath (place a bowl with the chocolate over a pot of gently simmering water, making sure the bottom of the bowl does not touch the water) or in the microwave (in short, 15-second intervals, stirring each time). Set aside to cool slightly.

In a large bowl, place the mascarpone cheese and briefly mix it to loosen its texture. Add the cooled white chocolate and mix until combined. Then, while continuously mixing on low speed, slowly pour in the strawberry puree with gelatin. Mix only until you achieve a smooth, pink mixture.

In a separate, clean, and well-chilled bowl, whip the cold 36% cream with the sifted powdered sugar (80g) until stiff peaks form. Be careful not to 'overwhip' it (it will turn into butter). Add the whipped cream to the strawberry mixture in two batches. Mix the first batch more vigorously to loosen the mixture, and gently fold in the second batch with a spatula, just like you would with flour for a sponge cake, to keep the mousse fluffy.

Melt 150g of white chocolate in a water bath and set aside to cool completely. In a mixing bowl, place very soft butter and sifted 50g of powdered sugar. Beat on high speed for 7-8 minutes until the mixture becomes very light, fluffy, and doubles in volume. This process is called aerating the butter.

Add cold cream cheese to the fluffy butter in batches, one tablespoon at a time. Mix on medium speed just until the ingredients are combined after each addition. Finally, while continuing to mix, pour in the cooled white chocolate in a thin stream. Mix briefly until you achieve a smooth, uniform cream.

Place the first layer of sponge cake on a platter or plate. Tighten an adjustable pastry ring around it, lined on the inside with acetate (this will ensure the sides of the cake are perfectly smooth). Evenly soak the sponge with half of the prepared syrup, using a brush or teaspoon.

Pour the entire strawberry mousse onto the soaked layer. Smooth the surface with a spatula. Cover with the second layer of sponge cake, pressing it down gently. Soak it with the remaining syrup. Place the prepared cake in the refrigerator for at least 4-6 hours, preferably overnight. The mousse must set completely.

When the cake is well chilled, carefully remove the pastry ring and the plastic wrap. Using a spatula, spread a thin layer of the prepared cream on the top and sides of the cake. This is called a 'crumb coat', which 'catches' all the crumbs. Place the cake in the refrigerator for 30 minutes to let this layer set.

Take the cake out of the fridge and apply the remaining cream, creating a smooth final layer. Smooth the sides and top using a spatula or a special pastry scraper. Finally, decorate the cake with fresh strawberries (the remaining 250g), mint leaves, and optionally toasted almond flakes. Store in the fridge.