# Mix softened butter, thinly grated kasar 
cheese, 
yogurt and egg white in a deep bowl by a fork until it turns into homogenous.
# Add very thinly chopped uncooked 
spinach, salt, the mixture of baking powder with some 
flour and mix it for a while more.
# Knead the mixture by adding 
flour in it little by little. Make the dough stop sticking to your hands. Then rest it for about 10 minutes. 
# Pick 
walnut sized pieces from the dough. Shape them over the bench as pencils. 
# Fold the dough bar from the middle and twist it around itself for 2 times.
# Transfer the cookies into a greased baking tray. Spread yolk all over and sprinkle nigella.
# Place the tray into the oven which is preheated to 390 F. Bake them until they turn into red.