How to make
Beat 5 egg whites with 2/5 cup (100 g) powdered sugar into a thick cream. In another bowl, beat 5 yolks with 3 1/3 tbsp (50 g) powdered sugar to a thick snow. Carefully mix the beaten whites and yolks. Add the water, sifted flour and cocoa with the baking powder. Knead until homogeneous.
Distribute the mixture into a rectangular tray with baking paper, smooth it out and bake in a 360°F (180 °C) oven about 20 min. Remove the layer from the tray and cool it.
Heat the milk with the powdered sugar in a thick-bottomed pot. Pour the starch, diluted in a little milk, in a thin trickle and the beaten yolks. Stir constantly on low heat until the cream thickens. Cool.
In a separate container, beat the butter with the powdered sugar into fluffy cream. The butter needs to be at room temperature. Add the buttercream to the now cooled vanilla cream. Stir carefully until both mixtures combine.
Place the layer in a suitable platter. Smear it generously with the somewhat hardened cream. Smear with blueberry jam on top. Beat the egg whites with the sugar to thick snow and smear it over the blueberry jam.
Finish it off by sprinkling with grated cheese. Before serving, leave for 2-3 hours to cool in the fridge.
