Delicious Coffee Cake

For the Coffee Sponge Cake: Beat egg whites stiff with a pinch of salt. Gradually add sugar. Blend egg yolks with vinegar and baking powder, add to the mixture. Pour in oil, mix briefly. Combine sifted flour with coffee. Gently fold into the egg mixture. Pour into a pan. Bake at 180 degrees Celsius for 25 minutes.
For the Light Sponge Cake: Beat egg whites stiff, gradually adding sugar. Add egg yolks one by one and mix until combined. Gradually mix in oil. Sift flour into the mixture, gently fold with a spatula. Pour the batter into a pan of the same size as the coffee cake.
For the Custard Cream: Pour half a cup of milk, add a tablespoon of wheat flour, and cornstarch, and both types of sugar. Mix well. Bring the rest of the milk together with regular sugar to a boil. Once boiling, pour in the milk and flour mixture, stirring constantly, cook the custard until thickened. Then add cold butter cut into smaller pieces and stir until melted!