Finely crumble the biscuits in the universal chopper. Mix flour, brown sugar, 1 pinch of salt and biscuit crumbs, add 50 g butter in flakes and knead with the dough hooks of the hand mixer, then form into a smooth dough with your hands.
Press the dough into a greased springform pan (20 cm Ø), forming a rim of about 3 cm. Chill for about 30 minutes.
Pre-bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 10 minutes on the bottom shelf. Melt the remaining butter. Beat the egg, egg yolks, vanillin sugar and sugar until creamy with the whisks of the hand mixer.
Add starch, butter, cream cheese, mascarpone and liqueur and stir in carefully. Put the mixture in a cool place.
Remove the base from the oven and let it cool down for about 20 minutes. Spread 4 tbsp. jam on the base, add the cheese mixture. Half fill a deep baking tray with hot water. Wrap the springform pan with foil so that no water gets into the pan.
Place the springform pan on the baking tray and bake again at the same temperature in the preheated oven for about 30 minutes.
Remove from the oven, remove foil, let it cool down and chill for about 4 hours. Sort the blackberries. Heat the rest of the jam in a pot and mix with the blackberries. Carefully remove the cake from the tin, spread the blackberries on top and serve.