01 -
Preheat oven to 425°F. Toss pepper halves with 1 tablespoon olive oil, ½ teaspoon salt, and ¼ teaspoon black pepper. Arrange cut side up on a lined baking sheet and roast for 10 minutes until edges soften. Drain any released liquid and set aside.
02 -
Heat 1 tablespoon olive oil in a large skillet over medium-high heat until shimmering. Add mushrooms in an even layer and cook undisturbed for 2 minutes to brown. Add sliced onion and a pinch of salt, sautéing until onions are tender and lightly caramelized, about 5 to 6 minutes. Push vegetables to pan edges.
03 -
Add ground beef to the center of the skillet and sear for 2 minutes before breaking it up. Cook until mostly browned, 3 to 4 minutes, then drain excess fat if necessary. Stir in Worcestershire sauce, garlic powder, ½ teaspoon salt, ¼ teaspoon black pepper, and Italian seasoning. Fold mushrooms and onions back in, cook 1 minute more until glossy. Remove from heat.
04 -
Lower oven temperature to 400°F. Blot any moisture inside pepper halves with paper towel. Sprinkle a thin layer of shredded provolone at the bottom of each pepper as a moisture barrier. Fill peppers evenly with beef mixture, gently packing, then top each with remaining provolone and mozzarella.
05 -
Bake stuffed peppers for 10 to 12 minutes until peppers are fork-tender and cheese is melted and bubbly. For browned cheese spots, broil for 1 to 2 minutes while watching closely.
06 -
Allow stuffed peppers to rest for 5 minutes to let juices settle and filling firm up. Finish with freshly cracked black pepper and serve warm.