Mix 250 g flour, starch, salt, baking powder, 75 g sugar, vanillin sugar, 3 eggs, 100 ml milk and 200 g butter with the whisk of the hand mixer to a smooth dough. Halve the dough. Stir 25 ml milk, 2 tablespoons sugar and cocoa into one half of the dough
Grease a springform pan (26 cm Ø) and dust with flour. Spread the dough alternately in the springform pan. Use a fork to draw through the dough spirally and smooth it down. Wash the orange and rub dry. Grate the skin thinly. Knead 75 g butter, 50 g sugar, 175 g flour, 1 egg and orange zest into crumbles
Spread the frozen berries evenly on the dough and press lightly. Sprinkle with crumbles. Bake the cake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 1 hour. Remove and let cool on a cake rack. Dust with icing sugar and cut into pieces
waiting time approx. 2 hours