*500 mL thick kefir
*1 tbsp sugar
*1 tsp salt
* 200 grams butter
*4 cups flour
*1 tsp. dry yeast
*1/3 cup vegetable oil
1) Combine and carefully mix milk and dry yeast, salt and sugar, and leave it all for about five minutes. Melt the butter in a small pot. Crack the egg into the melted butter, then pour the kefir and yeast over it. Add flour and then the vegetable oil to the mixture. Knead the dough.
2) Cover the dough with a plastic wrap and put it in the refrigerator for about an hour.
3) Heat in the oven to 180 degrees Celsius. Press the dough into a thin circle, then cut the circle into eight even triangles.
4) Roll the croissants from bottom to top. Put the rolled croissants into a baking pan.
5) Rub the surface of the croissants with a mixture of egg yolk and sugar. Bake in the oven for 15-20 minutes at 200 degrees Celsius.