Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Fold a piece of aluminium foil into a firm strip of approx. 5 x 32 cm. Use the strip to divide a fat pan (deep baking tray) crosswise into two halves.
Half a fat one. Melt 150 g butter. Finely crumble 400 g biscuits, mix with the melted butter. Put the crumb mixture on the greased side of the tray and press it to a flat bottom.
Bake in a hot oven for about 8 minutes. Take out and let cool down.
For the cookie dough, stir 50 g butter, brown sugar, 1 tablespoon white sugar and 1 pinch of salt until creamy. Stir in flour. Knead in half the chocolate drops, put the dough aside.
Chop 200 g biscuits into pieces. For the cheesecake mixture, stir cream cheese, sour cream, 100 g sugar and vanilla sugar until smooth. Stir in the starch and eggs one after the other, fold in the cookie pieces.
Spread the mixture on the floor. Pluck the cookie dough into small pieces and spread on the cheesecake mixture. Sprinkle with remaining chocolate drops. Bake in a hot oven for 40-45 minutes.