In a large skillet brown the ground beef with onion, garlic, bell pepper, oregano and chili flakes (if using) drain fat, season with seasoned salt and black pepper, then mix in 1/4-1/3 cup grated Parmesan cheese.
Stir in the tomato sauce and mushrooms; simmer for about 10-12 minutes.
Unroll one package of crescent rolls and separate the dough in triangles; arrange the triangles with pointed ends to the center, then press the edges together to form a pie shell.
In a bowl beat together 2 egg yolks and 3 egg whites until well combined.
Pour HALF of the egg mixture over the pie shell.
Spoon the meat mixture into the shell over the egg mixture.
Arrange the cheese slices over the beef mixture, then top with remaining beaten egg mixture.
Unroll the second crescent roll package, then place four sections of dough together to form a 12x16-inch rectangle; press edges and perforations together, then roll the dough into a 12-inch square.
In a small bowl whisk 1 egg yolk with 1 tablespoon cold water.
Brush the edges of bottom crust with yolk/water mixture, then place the dough on top of the beef filling; trim, seal and flute edges.
Cut small two slits in top of the crust, then brush the top dough with yolk/water mixture; sprinkle with about 2 tablespoons grated Parmesan cheese if desired.
Loosley cover the edge with a foil strip to prevent browning.
Bake at 350 degrees for about 20 minutes.
Cover the center of the pie loosley with foil and continue to bake for about 20 minutes longer.