2 packets of phyllo dough (Bulgarian "fini kori" or phyllo from the frozen desserts section)
200 grams of yellow cheese (Bulgarian kashkaval or a mixture of cheddar and mozzarelle)
500 grams of white cheese (Bulgarian sirene or feta cheese)
100 grams of butter
1/2 cup of soda water
1 cup yogurt
Mix six of the eggs, the grated butter, the crumbled white cheese, the yellow cheese cut in small pieces, and the yogurt. In a buttered pan, lay a layer of the filo dough, spread a layer of the mixture. Finish with a layer of filo dough. Then cut the banitsa into serving pieces. Mix the last egg with the soda water and stir. Pour the mixture over the banitsa and make sure there are no pieces of the filo dough left dry. Bake in a preheated over at 200 C for 40 minutes, or till golden.