2 1/2 cups warm water (110 degrees F/45 degrees C)
2 tablespoons dried bread crumbs
1 1/8 teaspoons salt
1 1/4 teaspoons dry yeast
2 eggs, room temperature
2 1/2 teaspoons butter at room temperature
1 tablespoon unsalted butter, melted
5 cups all-purpose flour, divided
3 tablespoons bread flour, divided
2 tablespoons salt, divided
1 1/2 cups dry bread cubes
1/2 teaspoon vegetable oil
1 cup shredded mozzarella cheese
3/4 cup water, divided
Preheat oven to 350 degrees F (175 degrees C).
In a large bowl, stir together water, 1 tablespoon dried bread crumbs, salt, 1 tablespoon dried yeast, 2 eggs, butter and 2 tablespoons melted butter. Stir in 2 cups crushed yogurt.
In a separate bowl, dissolve 1/2 cup bread cubes in 2 tablespoons water and set aside. In a small bowl, stir together gelatin and 1 cup of yogurt; set aside.
Mix remaining bread cubes and melted butter in a small bowl. Stir flour mixture into the sauce mixture, and spoon the excess into the dough. Stir in 1 cup of cheese, 1 cup water, 3 cups of the mashed sourdough starter, 1 cup of the cream cheese mixture, and 1 cup milk. Chill dough overnight, then remove from freezer.
Preheat oven to 350 degrees F (175 degrees C). Lightly grease 6 baking sheets.
Bake in preheated oven for 60 minutes, until golden brown and firm.
Stir gelatin mixture into cold water to come to a boil; remove from heat. In a medium bowl, beat the remaining butter and milk until smooth.
Pour 1/3 water into a large bowl, and beat the egg whites until soft peaks form. Add 1 cup of reserved white mashed sourdough starter, 1 cup cream, and 1 teaspoon of milk; beat until stiff peaks form. Scrape bowl, and set aside. Continue this process with remaining 1 cup of sourdough starter, 1 cup cream, and 1 teaspoon milk; beat until well blended. Stir in the 1/3 water, and stir. In a small bowl, quickly fold 1/3 of the egg whites into the whites. Stir in 1/3 of the egg white mixture, and fold in remaining sourdough starter, 1 cup cream, and 1 teaspoon milk. Transfer the dough to a greased bowl, and divide in half.
Make dough surface level with a well floured fork. Pat one layer of dough evenly into the bottom of a 9x13 inch baking pan. Sprinkle one layer with 3/4 cup of the cream cheese mixture. Spread over the cream cheese layer, and press down slightly so as not to press them together. Spread the remaining pastries evenly over the cream cheese layer, and press down slightly as well. Spread remaining cream over this layer, and pour the remaining 1/4 of the cream over the top. Fold off half, and press down slightly as well. Cut into 12 triangles, fold over the dough. Press one triangle into the bottom of the pan. Turn and press one more down over the top. Bake for 45 to 50 minutes, or until golden brown. Cool on wire racks. To make the Feta Cheese: In a large bowl, beat together 1/2 cup cream cheese, 1/2 teaspoon salt, and 1/2 teaspoon garlic powder until smooth. Whip in 1/2 cup water. Stir in 1 1/2