How To Make It :
First prepare your egg custard.
Add the yolk, starch and sugar to the milk. Put the pot on the stove and stir until the custard thickens.
Remove it from the heat and flavor the custard with a vanilla.
Crack the eggs into a bowl, add the sugar and beat them with a mixer until a thick custard is obtained.
Sift the flour with a teaspoon of baking powder, a vanilla and a pinch of salt.
Add them in portions to the egg mixture, while stirring with a spoon.
Line a small oblong baking tray with parchment paper. Pour the sponge cake mixture into it.
Even out and spread the cream on top in 6 piles.
Bake the sponge cake at 360°F (180°C) for 10-12 minutes in a preheated oven.
Let the baked sponge cake with egg custard cool down and sprinkle it with powdered sugar. Cut it into squares.
Enjoy!
Source : Allrecipes.Com