How to make
Put 12 1/2 cups (3 liters) of salted water in a pot and add the baking soda. Stir to dissolve the salt and baking soda. Immerse each phyllo pastry sheet in this liquid. Melt the butter until it becomes clear and strain it. Beat the eggs with the yoghurt and feta cheese.
Butter a tray thoroughly and place 2 phyllo pastry sheets that have been submerged and drained from the salted soda water. Distribute the filling on top and then place 2 more sheets. Repeat this process until you run out of products. Brush the last sheet with plenty of butter and leave the pastry to rest for 30 minutes.
Then, put it to bake in a moderate oven at about 340°F (170 °C) for about 30 minutes. After removing the baked Botevgrad phyllo pastry from the oven, sprinkle it with a little water and wrap it with a towel to smother.