Knead flour, fat in pieces, 60 g sugar, salt, egg and 1 tablespoon cold water first with the dough hooks of the hand mixer, then briefly with your hands. Cover and chill for approx. 30 minutes.
Sort the berries, wash if necessary and dab dry. Strip the currants from the stems with a fork. Mix pudding powder and 1/8 l milk until smooth. Boil up the rest of the milk. Stir in pudding powder, 125 g sugar and vanilla sugar and bring to the boil briefly. Cool briefly (approx. 2 minutes). Stir in sour cream
Grease a tart or springform pan (26 cm Ø). Roll out the dough on a little flour until round (approx. 30 cm Ø). Put it into the tin and press it up 2-3 cm at the edge. Prick the base several times. Spread half of the sour cream mixture on the base. Spread 2/3 of the berries on top. Spread the rest of the sour cream mixture on top.
Bake in the preheated oven (electric oven: 175 °C / convection oven: 150 °C / gas: level 2) for about 1 1/4 hours. Cool down, place in a cool place overnight. Sprinkle with the rest of the berries and dust with icing sugar