Knead butter in flakes, flour, 1 egg and 50 g sugar to a smooth dough. Cover and chill for about 30 minutes. In the meantime peel apples, quarter them and cut out the core. Cut the fruit flesh into fine slices.
Sprinkle with lemon juice, bring to the boil briefly, cool and allow to drip off. Roll out the dough on a lightly floured work surface until round (30 cm Ø). Place in a greased springform pan (26 cm Ø).
Press edges together. Prick the base several times with a fork, sprinkle with breadcrumbs and spread apples on top. Mix pudding powder, cream, sour cream, 50 g sugar and 3 eggs. Pour over the apples.
Sprinkle with flaked almonds and 2 tablespoons of sugar. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 45-50 minutes. Leave to cool in the mould on a rack.
Serve dusted with icing sugar.