Grease square (24 x 24 cm) or round springform pan (26 cm Ø) and dust with flour. Mix flour, cocoa, baking powder and 125 g sugar. Add butter in flakes, 1 egg and lemon juice. Knead everything first with the dough hooks of the hand mixer and then briefly with your hands to form crumbles. Chill for about 10 minutes
Drain the mandarin oranges. Mix cream cheese, sour cream, 3 eggs, 125 g sugar, vanillin sugar and pudding powder briefly. Fold in the mandarins
Spread 3/4 of the crumble as a base in the mould and press on. Spread the cheese mixture on top. Sprinkle the rest of the crumbles on top, rubbing or pulling between your fingers
Bake in the preheated oven (electric oven: 200 °C/circulating air: 175 °C/gas: level 3) for about 1 hour. Leave to cool in the mould. Dust with cocoa