It is best to make the crumble first so that the mass can solidify again. To do this, let the butter melt in a pan and heat until it is lightly browned (nut butter). Mix with flour, sugar and vanilla sugar and let it set again.
For the dough, put the flour in a bowl, make a well in the middle, crumble in the yeast, add half of the sugar and stir in a little lukewarm milk until smooth. Let the pre-dough rise in a warm place until its volume has doubled.
Then knead into a smooth dough with the remaining flour, sugar, vanilla sugar, milk and an egg. Let this rise in a warm place until the volume has doubled. Then the dough is rolled out on a greased baking sheet. Fill the poppy seed bakery in the middle on a strip approx. Spread the streusel over it and bake at approx. 180 degrees in the preheated oven for approx. 40 minutes.