For the quick and easy sponge cookies, beat 4 egg whites, 3 tablespoons cold water, vanilla sugar and the cane sugar until fluffy. Add the flour and place on a baking tray (it should be about 1 cm thick).
Bake in the oven at 180°C for 20 minutes. When cool, cover with the chocolate melted in the microwave or in a water bath. When the chocolate has hardened, cut into small pieces. Serve the sponge cookies.