Mix the quark well with the milk, oil, egg, sugar and lemon zest. Then sieve the flour and mix it with the baking powder. Then knead both to a smooth dough, ideally with the dough hook. Let rest for 30 minutes.
Shape the dough into small croissants and place on a baking sheet. Brush the croissants with half of the melted butter. Bake at 200 ° for about 10 minutes, the croissants must not turn brown.
After baking, brush immediately with the remaining butter and toss in the sugar and vanilla flavor.