For the doughnut, first prepare a dampfl. Mix 10 ml lukewarm milk, yeast, 10 g sugar and 150 g flour and let it rise in a warm place until it doubles in size.
Put all the other dough ingredients on a board and empty the dampfl into the middle, work into a smooth dough. Leave to rest for a while.
Roll out the dough, cut out doughnuts and shape into balls of as equal size as possible. Place on a floured board, and let rise again.
Then fry in hot oil for about 3 minutes on each side. Let cool , then fill with vanilla cream and frost the top.
For the cream, heat the milk with sugar, vanilla sugar and lemon zest, stir in custard powder, bring to a boil, then mix in the whipped cream and let cool.
For the glaze, heat the water and mix the sugar well in it.