Put 375 g flour in a bowl. Press a depression in the middle. Warm 150 ml milk and 1 tablespoon sugar lukewarm. Crumble yeast into it, dissolve. Pour into the hollow, mix with some of the flour to make a pre-dough. Cover and leave to rise in a warm place for 15-20 minutes
Add 50 g butter, 1 egg, 2 tablespoons sugar and 1/4 level teaspoon salt to the pre-dough. Knead everything smooth with the hand mixer. Cover the dough and let it rise in a warm place for 45-60 minutes
Separate 4 eggs, chill the egg white. Boil up 1 l milk, 200 g sugar, 1 vanillin sugar and lemon peel. Stir in semolina, cover and let it swell at low heat for 10-12 minutes until it is thick and creamy. Pull the pot off the stove
Mix 6 tablespoons of 1/2 l milk with pudding powder and 50 g sugar. Boil up the remaining milk. Stir in pudding powder and simmer for 1-2 minutes while stirring. Stir into the hot semolina. Stir in 4 egg yolks one after the other. Beat 4 egg whites and 1 pinch of salt until stiff. Stir the beaten egg whites into the hot pudding. Let cool down a little bit
Grease a fat pan (approx. 32 x 39 cm, at least 3.5 cm deep) and dust with a little flour. Knead the dough again briefly. Roll out on the fat pan and press up the edge a little. Cover and let rise for another 15 minutes.
Separate two eggs. Beat 2 egg whites and 1 pinch of salt until stiff. Mix the sour cream, 2 egg yolks and 1 vanilla sugar. Fold in the beaten egg whites. Spread the pudding, then the custard mixture on the dough. Bake in the preheated oven (electric oven: 200 °C/circulating air: 175 °C/gas: level 3) on the middle shelf for about 35 minutes. Let them cool down. Dust with icing sugar