Carefully cut the spongecake into three horizontal layers.
Strawberries: Save half of the strawberries for decoration. Cut the other half of the strawberries in small cubes — an put in a bowl. Mix in the sugar og let it rest until the sugar has dissolved. It should become a little sirupy.
Vanilla Custard: Bring the milk, with the vanilla bean added, to a boil. Whisk the egg yolks with the sugar and corn starch. Add 1 tablespoon of water if the mixture becomes too thick. Remove the vanilla bean and then pour the milk over the egg mixture and whisk brisklyl. Pour the mixture back into the pot. Gently reheat the mixture and continue whisking until it becomes a thick cream. Pour the cream through a sieve and let cool. Whip 2/3 cup of the heavy cream and fold it in the custard.
Spread half of the vanilla custard and then half of the strawberry filling on the bottom layer of the sponge cake. Place the second layer on top of this and press gently. Repeat the above process before placing the last layer of sponge cake on top.
Tip! If you have extra time on your hands, you may cover the cake in plastic wrap and place it in the refrigerator for 24 hours before decorating. This will give the flavours time to settle a bit and will make a great cake even better!
For serving: Whip the remaining cream. Use a pastry bag with a spout to decorate, working it in an upward movement all around the cake. To crown the work add the remaining strawberries on top.