1
First, prepare the strawberry insert, as it needs to set well. Soak the gelatine sheets in cold water for at least 5 minutes. Heat the strawberries with the sugar until soft and mash them. Melt the seared gelatine leaves in the warm strawberry puree. Pour it into a ring or baking dish 14 cm in diameter (4 cm less than the diameter of the cake), which you have lined with cling film and sealed well. Place in the freezer to set.
2
Preheat the oven to 180°C. Beat the eggs with the sugar and vanilla paste on high speed for 10 minutes. Sift the flour over the egg mixture and fold in gently with a spatula. Spread the mixture on an 18 cm diameter baking tray lined with baking paper (bottom) and bake for 15 minutes. While the sponge cake is baking, prepare the sugar solution. Remove the baked sponge cake from the baking tray and cool on a wire rack.
3
While the sponge cake is baking, make the vanilla custard by bringing 1 dl of milk to the boil and whisking the remaining milk smooth with the egg, sugar, vanilla and starch. Add the egg mixture to the milk and cook for about 5 minutes, stirring, until the custard thickens - it is important to stir constantly with a whisk while cooking. Remove from the heat, add the butter and stir until melted. Soak the gelatine in cold water for 5 minutes, then strain and melt in the warm cream. Cover the custard with plastic wrap so that it is touching and cool until lukewarm. Whip the sweet cream and put it in a cold place. Blend the cooled cream smooth, add it to the cream in two steps and fold in with a spatula.
4
Cut the sponge cake into two equal discs. Trim the upper one to a size of 14 cm (4 cm less than the diameter of the cake). Place the lower sponge on the base, moisten it and place the ring on it. Spread it with less than half of the cream; place the smaller sponge on top of the cream, moisten it and place the frozen strawberry insert on top. Spread the rest of the cream over the sponge, making sure to fill the rim around the sponge first. Level the surface and put the cake in the fridge to firm up the cream.
5
Boil the strawberries with the water and sugar. Soak the gelatine in cold water for 5 minutes. Grind the strawberries into a puree, cool it slightly (it must not be too hot) and dissolve the strained gelatine in it. Pour the lukewarm puree over the cold custard and refrigerate the cake for at least 4 hours. Remove the ring from the cooled cake and decorate as desired.