Chocolate-vanilla layer cake

I was craving something sweet and chocolatey. This took less than an hour to whip up.

Ingredients
cake:
4 eggs
4 tbsp flour
4 leveled tbsp sugar
1 tsp baking powder
0.5 tbsp vanilla sugar

filling:
8 oz semi-sweet Ghirardelli chocolate bar
1.5 tbsp corn starch
2 tbsp sugar
1 tbsp Ghirardelli cocoa powder
pinch of salt
1 cup milk
0.5 tsp vanilla extract

Preparation
Shred the chocolate bar.

Line a 15x10 baking sheet with good, nonstick baking paper. Beat the eggs with the sugar and vanilla sugar until white and fluffy. Add the flour mixed with the baking powder and continue beating. Pour onto the parchment paper and bake in a preheated 350F oven without opening the oven door for about 10 minutes, continue baking until the edges are slightly browned. Cool in the oven for a few minutes before removing from the pan and peeling off the parchment paper.

Meanwhile, mix the dry ingredients with the exception of the chocolate for the filling. Stir in the milk and bring to a boil gently. Stir until the filling thickens. This will only take a few minutes from the moment boiling was reached. Stir in the shredded chocolate and the vanilla.

Using a ruler, cut the cake sheet into 3 equal slices. Cut these in half (not as shown in the picture). Spread each sheet with cream and assemble. Coat the outside and sprinkle with unsweetened cocoa. Slice and serve with whipped cream.