Prep the peppers: Preheat your oven to 400°F (200°C). Halve the bell peppers lengthwise and remove seeds and membranes. Brush with oil, season with salt and pepper, and place cut side up on a baking sheet. Roast for 12–15 minutes until slightly tender but still holding shape.

Slice the beef: If not pre-sliced, freeze the steak for 20–30 minutes to firm it up, then slice very thin against the grain. Season with salt and pepper.

Sauté the vegetables: Heat a large skillet over medium-high heat. Add 1 tablespoon oil and the butter. Toss in onions and mushrooms with a pinch of salt. Cook, stirring, for 6–8 minutes until the onions are soft and the mushrooms release their moisture and brown slightly. Add garlic and cook 30 seconds more.

Deglaze: Pour in the beef broth and Worcestershire. Scrape up browned bits and let the liquid reduce by half, about 2 minutes. Transfer the veggie mix to a bowl.

Cook the beef: Add a touch more oil to the hot pan. Spread the beef in a single layer. Sear for 1–2 minutes per side until just cooked through. Avoid overcooking, which can make it tough.

Combine: Return the onions and mushrooms to the pan with the beef. Toss to combine and taste. Adjust salt, pepper, or add red pepper flakes for heat.

Assemble the peppers: Remove peppers from the oven. Lay a slice of provolone in each pepper half. Spoon in the beef mixture, packing it neatly. Top with another slice of provolone.

Bake to melt: Return the stuffed peppers to the oven for 6–8 minutes, until the cheese is melted and lightly golden at the edges. For extra browning, broil for 1–2 minutes, watching closely.

Finish and serve: Let rest for 3–5 minutes. Garnish with chopped parsley or sliced jalapeños if you like. Serve hot.