Dough: Add dry yeast and sugar to the cup of warm milk(not hot) and wait for 5min.
Shift the flower, put it in a bigger bowl, add baking powder and salt. Then add oil, Greek yogurt and sour cream. When yeast is bubbly enough add it to the mixture, knead it with hands or with hand mixer until you get an even and compact dough(until it starts separating from the bowl and form a ball). Put it to rest in a greased bowl for at least 10min.
2
Put little bit of flour onto the work surface. Divide the dough in 4pcs and roll the first one with rolling pin (about 5mm) on the work surface (make it round shape). When it's thin, cut it with knife in 8 even triangle shapes. Put the filling on every triangle together with little bit of butter on each. Roll it into croissant shape. Do the same with the remaining three doughs and put it on the baking tray sprinkled with oil beforehand. Preheat the oven to 180 degrees.
3
Brush the top of each roll bread with egg yolk and sprinkle with sesame, other seed or ground salt as you like. Put pieces of butter in gaps between rolls because it adds to the flavour.