Slice peppers in half lengthwise, remove ribs and seeds. To make the individual. cups
Preheat oven to 400*
Slice onions and mushrooms and saute over medium heat with olive oil in a large skillet. Add garlic and a little salt and pepper. You want to saute until onions and mushroom are nice and caramelized. About 15 minutes.
Add sliced beef to the skillet with the onion/mushroom mixture. Allow to cook 5-10 minutes or until fully cooked.
Line the inside of each pepper with a slice of provolone cheese and then fill each pepper with meat mixture until they are nearly overflowing.
Top each pepper with another slice of provolone cheese.
Place in baking dish and bake for 15-20 minutes until the cheese on top is golden brown.