Directions

1. Preheat oven to 375 degrees F (190 degrees C).
2. Brown beef in a large skillet over medium-high heat. Halfway through browning, add mushrooms and onion. Continue cooking until meat is fully browned; drain fat from skillet. Stir in enough gravy to bond mixture without making it soupy. Season with salt and pepper, and set aside.
3. Meanwhile, heat a medium saucepan of water until boiling. Place peppers in water, and boil for 2 to 3 minutes, until just tender; remove from water. Place peppers, hollow side up, in a 9x13 inch baking dish, and fill each with beef mixture.
4. Bake in preheated oven for 15 to 20 minutes, until bubbling. Top with cheese, and bake for an additional 5 to 10 minutes. Serve in a small pool of gravy.