Preheat oven to 320 °F (160 °C).

Grind the marzipan finely and mix well with water, eggs, and confectioner’s sugar.

Mix together flour, cornstarch, vanilla sugar, and a dash of salt and carefully mix into the marzipan.

Stir in the melted butter along with the candied orange peel and orange zest.

Fill a baking frame or a deep, buttered cake pan.

Cut the oranges into slices, dust the slices with some flour, and lay on top of the batter.

Bake for about 45 minutes.

Let cool.

Mix Cointreau with orange marmalade and brush on the cake.

For the cream, melt both chocolates to lukewarm and mix with the room temperature butter.

Add the Cointreau and cream the whole mixture.

Spread the cream on the cake, draw a decorative pattern, and chill.

Dust with cocoa powder and serve.