In a large bowl, combine the ground beef, ground pork, bread crumbs, eggs, onion, green bell pepper, salt, ground black pepper, Italian-style seasoning, sage, garlic powder, 1/2 cup pizza sauce and stewed tomatoes. Mix well and form into 24 patties using a 1/4 cup measuring cup OR an ice cream scoop.
In a separate small bowl, combine the mushrooms and olives and set aside. Arrange 12 patties on 2 ungreased baking sheets. Place 4 slices of pepperoni on each patty, then a small amount of the mushroom olive mixture, and then a slice of mozzarella cheese. Top each patty off with another patty and pinch the edges all around to seal everything into the middle. Finally, top each with a drizzle of remaining pizza sauce and some shredded mozzarella cheese.
Bake at 375 degrees F (190 degrees C) for 30 to 40 minutes.
