Grease a springform pan (26 cm Ø). Melt the butter and cool down a little. Pour the lady fingers into a freezer bag and close the bag. Crumble the biscuits finely with a dough roll. Mix the biscuits with butter and cocoa. Spread on the bottom of the mould and press on. Cool for about 30 minutes.
Beat the eggs, 200 g sugar and vanillin sugar until fluffy. Stir in cream cheese, cream, starch and orange peel. Spread the cheese mixture on the sponge cake base. Bake in the preheated oven (electric cooker: 175 °C / convection oven: 150 °C /gas: level 2) for about 1 hour
Remove the cake from the oven and let it cool in the mould on a cake rack for about 10 minutes. Mix crème fraîche and 1 tablespoon of sugar. Spread on the cake and bake at the same temperature for another 10 minutes. Let it cool down