Spread a thin layer of oil on the bottom of a springform pan (26 cm Ø) and grease the rim. Melt butter. Finely chop 20 biscuits in a food processor and mix well with the hot butter.
Spread the mixture on the bottom of the springform pan and press it down with a spoon. Chill for about 30 minutes.
Carefully unscrew the remaining biscuits, scrape off the filling and place in a bowl. Place approx. 17 biscuit halves upright inside on the rim of the springform pan.
Cream quark, cream cheese, sugar, vanillin sugar, orange peel, cookie filling and flour. Add the eggs one by one and stir in. Put the mixture into the springform pan and smooth it down. Cover with remaining biscuit halves.
Bake in the preheated oven, 2nd shelf from below (electric oven: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for 45-50 minutes. Remove from the oven, remove carefully from the edge with a knife. Cool in the mould on a cake rack.
Cover and leave to cool overnight in the refrigerator or in a cool place.