For the Striezel, mix flour with dry yeast well. Add yolks, lemon zest, salt, vanilla sugar and rum.
Heat milk with butter and granulated sugar, mix with the other ingredients and knead well. Cover the dough on a floured board and let it rise for half an hour.
Then form a Striezel, put it on a baking tray covered with baking paper and let it rise again.
Before baking, brush the dough with beaten egg and sprinkle with sugar.
Bake the Striezel at 170° C.