Pour the lukewarm milk into a large bowl. Stir in the sugar, 1 tablespoon of flour and the yeast. Let it stand for 10 minutes.
Add in the baking powder, salt, vegetable oil, egg whites and 3 cups of flour. Stir with a wooden spoon until the dough is well mixed, then turn it out onto a lightly floured surface.
Knead the dough for 10 minutes, then put in a large bowl, cover it with a dish towel and allow it to rise for about 1 hour.
Preheat your oven to 375
Punch down the dough and knead for another 5 minutes until all the air is out.
Roll it into a log and cut it into 3 equal pieces
Take one piece and roll it out to about the size of a medium round pizza.
Cut the rolled out dough into 8 equal triangular slices, a pastry roller or pizza cutter works great for this.
Place a tablespoon of the feta cheese at the widest part of the triangle.
Beginning at the widest point of each slice, roll it toward the narrow tip.
Place on a lightly greased cookie sheet and continue until all the dough is used.
In a small mixing bowl, whisk the egg yolks and brush each croissant with the egg yolk.
Sprinkle with sesame seeds and place a few nobs of butter around the baking sheet
Bake for 15-20 minutes or until golden brown.
They are delicious, warm out of the oven
Enjoy with a shopska salad or tarator.