Dilute yeast in 100 grams of warm milk, add 1 tablespoon of sugar, sift 2 tablespoons of flour, mix, cover and leave for 20 minutes
Beat egg with sugar by hand. Sift flour into a deep bowl and mix with melted butter, egg-sugar mixture, salt, remaining milk and sourdough.
Knead the dough, cover with a towel and leave for 1 hour. The dough should increase in volume.
Once the dough to rise again to press down it.
Divide the dough into 2 parts and roll out 2 layers, 2 mm thick.
Each layer is cut into triangles.
With a wide side of the triangle to put 1.5 tbsp of the filling.
Spin each triangle into a roll. Lay a baking sheet with baking paper, put the workpiece. Leave on for 10-15 minutes.
Preheat the oven to 175 degrees and bake for 20 minutes. Cooled croissants sprinkle with powdered sugar.