Combine egg yolk with powdered sugar and beat to a pale yellow.
To the egg yolk, add some of the stiff egg whites, cornflour (corn starch), and all-purpose flour and fold in to combine. Repeat adding these ingredients alternatingly until you have added all the stiff whites and flours.
Also, fold in the cocoa powder and vanilla sugar (or vanilla extract) and combine to a smooth batter.
Pour the batter into a prepared cake pan.
Bake cake at 350° Fahrenheit/180° Celsius and let cool when finished baking.
Beat the whipping cream with the sugar to form stiff peaks.
Cut your cake into two pieces so that you are left with two same-sized cake rounds.
Place the bottom of your black forest cake on a cake plate/board or another surface.
Pour cherry liqueur equally all over the cake so that the alcohol gets soaked in.
Spread some of the whipping cream mass over the bottom cake layer.
Drop some of the cherries into the whipping cream layer.
Fit the second and top cake layer over the whipping cream/cherry layer.
Spread the remaining whipping cream over the top of the cake layer and spread around the cake too.
Sprinkle all the shaved chocolate pieces over the cake and to the side of the cake or decorate as you like.
Place remaining cherries on the cake to finish decorating.
Keep the cake in the fridge until serving time.
Cornfour is also known as corn starch or maizena or maize starch in some countries. This ingredient makes the cake fluffy but you can substitute it to 100% with all purpose four.
In Germany, vanilla sugar is common. 1 packet makes almost 2 Teaspoon or 7 grams. You can also substitute vanilla sugar with plain vanilla extract and add about 2 teaspoon plain powdered sugar extra.
The baked bottom cake layer needs to be soaked with cherry liqueur or so called Kirschwasser or else it's not a Black Forest Cake. You can also use cherry syrup if need be or other cherry brandy varieties.
For the cherries you can use fresh unpitted cherries in the cream laeyr and to top the cake. OR use canned pitted cherries in the creamy cake layer but whole fresh cherries to top the cake. Only fresh cherries look great to top the cake. Black FOrest Cake is usualy prepared with sour cherries such as Morello.