Drain the mandarins well and spread them on the cake base. Save a few tangerines for decoration later. Then whip the cream with the cream stiffener and sugar and mix with the quark and vanilla sugar until everything is creamy. Important: cream and quark should be nicely chilled. Then simply pour the quark cream mixture onto the mandarins and smooth everything out nicely with a large knife. Spread with the remaining mandarins and decorate with chocolate sprinkles.