Heat 1/8 l milk, add fat and melt. Mix yeast and 1 tablespoon of sugar. Put flour, quark, egg, remaining sugar, 2 sachets of vanillin sugar, yeast and the lukewarm milk-fat mixture into a bowl.
Mix to a smooth yeast dough with the dough hooks of the hand mixer. Cover and leave to rise in a warm place for about 40 minutes. Mix the remaining vanillin sugar and sugar crystals. Knead the yeast dough again and divide it into 15 equally sized pieces.
Form into croissants on a floured work surface, brush with milk and roll in decorating sugar. Place on two baking trays lined with baking paper. Bake one after the other in a preheated oven (electric: 175 °C/ gas: level 2) for 15-20 minutes until golden brown.
Let it cool down on a cake rack. Makes about 15 pieces.