Put the biscuits in a freezer bag and crumble them finely with a dough roll. Melt butter. Mix the cookie crumbs with the butter. Put them into a greased springform pan (26 cm Ø) and press them to a base, pressing up a small rim.
Mix pudding powder, sugar and vanilla sugar. Mix the quark and crème fraîche. Let the sugar mixture trickle in while stirring. Stir in eggs. Break chocolate bars into small pieces and stir into the cheese mixture, except for 2 bars. Fill the cheese mixture into the mould and bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 45 minutes. After about 20 minutes spread the remaining chocolate bars on the cake and continue baking.
Turn off the oven (do not open) and let the cake rest for about 1 hour. Take the cake out of the oven, remove from the edge of the mould and let it cool down. Remove the cake from the tin and arrange it.