Put flour, fat in small pieces, vanillin sugar, sour cream and baking powder on the work surface. Chop the ingredients well with a knife and knead quickly with cool hands.
Wrap in foil and chill for about 30 minutes. Drain the apricots and dice them finely. Coarsely chop the pistachio kernels. Separate egg, mix egg white, apricots and pistachios. Roll out the dough on a floured work surface to a rectangle of approx. 25 x 30 cm.
Spread apricot mixture on top. Carefully roll up the dough sheet from the long side. Cut the roll with a sharp knife into 10 pieces of approx. 3 cm width. Place the pieces on a baking tray lined with baking paper.
Whisk the egg yolk and milk together. Spread the snails with it. Bake in the preheated oven (electric: 200 °C/ gas: level 3) for about 30 minutes. Let the snails cool down a little on the tray. Warm up the apricot jam, pass through a sieve and coat the snails with it.
Let it dry on a cake rack. Makes about 10 pieces.