For the cake:
Heat oven to 375 F = 190 C
Line a 9" = 24 cm cake pan with a removable bottom with baking paper.
In a large bowl, whisk the flour with baking powder and cocoa powder.
Separate the egg whites and yolks from 3 eggs.
Beat egg whites with a whisk until you get a stiff foam.
Incorporate the sugar and vanilla sugar gradually and continue whisking until you get a dense and glossy meringue like mixture.
Incorporate the yolks, one by one, mixing gently with a spatula.
Incorporate all flour cocoa mixture, gradually. You should get an airy dough.
Pour it into the cake pan, level with a knife and bake for 20-25 minutes or until a toothpick comes out clean.
Remove from the oven and allow to completely cook into the cake pan.
For whipped cream:
I prefer the hand method but it takes a bit of an arm work so if you're not a fan, use a hand mixer (not a stand mixer, it doesn't whip through the bottom).
Place the sugar into the mixing bowl and add the whipping cream.
Whisk until the cream reaches stiff peaks.
Gently stir in the chocolate chips
Store any unused portion in an airtight container for up to 10 hours. When ready to use, rewhisk for a few seconds.
To assembly the cake:
When the cake has cooled completely, cut the top so that the base has 2" = 5 cm.
Using a spoon, make a hollow inside, leaving a 1" = 2.5 cm rim around the edges.
Set the crumbs aside.
Crumble into fine crumbs (I used my food processor).
Peel bananas, cut in slices and place them in the hollow formed inside the cake.
Place the whipped cream over bananas in a dome shape.
Sprinkle the fine crumbs all over.
Transfer to the fridge and chill for at least 2 hours then cut as you would a regular cake.