For the dough, sieve the flour into a mixing bowl and mix carefully with the yeast. Add sugar, vanilla sugar, salt, egg, milk and butter.
Process the ingredients with the hand mixer with dough hook first on the lowest setting, then on the highest setting in about 5 minutes to form a dough. Cover and leave the dough in a warm place until it has visibly enlarged (about 20-30 minutes).
For the streusel, sieve the flour into a mixing bowl. Add sugar, vanilla sugar and butter. Process the ingredients with the hand mixer with dough hook or with your hands into sprinkles of the desired size. Put half of the streusel in another bowl, work under the remaining streusel with cocoa powder. Chill the sprinkles until they are used again.
For the pudding from pudding powder, sugar and orange juice, prepare a pudding according to the package instructions, but with the ingredients listed here and let it cool, stirring occasionally. Then stir in the sour cream or crème fraîche.
Dust the dough lightly with flour, take it out of the bowl, knead again briefly on the lightly floured work surface and roll out on a greased baking sheet.
Put the pudding mixture on top and smooth it out. Spread the sprinkles on top. Let the dough rise again until it has visibly enlarged. Then bake the baking sheet in the oven at 180-200 ° C for about 25 minutes.