Cut the cold butter into small pieces, mix with the sugar, 2 eggs, flour and baking powder to make sprinkles (I always use the hand mixer and knead everything again with my hands). Distribute 2/3 of the amount on the greased tray and press firmly.
Then mix the quark, vanilla sugar, the remaining eggs and the custard powder with the whisk, mix in the drained mandarins. Spread the quark mixture on the crumble base and pour the remaining crumble on top.
Bake in a preheated oven at 180 ° C (top / bottom heat, convection: 160 ° C, gas: level 3) for approx. 35 minutes.