Heat oven to 350

Cut each top off the peppers and remove seeds and membranes. Rinse. Boil a pot of water big enough to cover peppers and once the water is boiling add peppers and boil for 2 minutes. Drain.

Take the sausage and chop it until it's like ground meat. Add to a skillet with chopped onion and continue breaking up into small pieces. Cook for about 8 to 10 minutes then mix together with rice, garlic, and tomato sauce. Save a tiny bit of tomato sauce for next step.

Add a small amount of tomato sauce to the bottom of a 9x12 casserole dish, just enough to coat the bottom slightly. Place peppers in dish and stuff with mixture. Cover dish tightly with foil and bake for 10 minutes. Remove foil then bake for 15 minutes. Sprinkle with mozzarella cheese for last 5 minutes.