Heat olive oil and butter in a large skillet over medium-high heat. Add sliced onions, peppers, and mushrooms. Sauté until onions are translucent and peppers have charred edges. Stir in garlic at the last minute. Remove veggies from the pan and set aside.

In the same skillet, increase the heat slightly. Add beef strips, season generously with salt and pepper. Cook for 2-3 minutes until browned. Remove from heat.

Preheat oven to 400 degrees Fahrenheit. Lay out cheese slices on a parchment-lined baking sheet.

Place a small mound of steak and vegetable mixture in the center of each cheese slice. Do not overfill.

Slide the tray into the oven for 5-7 minutes. Watch closely to ensure the cheese melts and edges turn golden and crispy.

Let the rolls sit for about 60 seconds. Use a spatula to roll the cheese around the filling while warm and pliable. Let cool for another minute before serving.

Sprinkle with extra parmesan or fresh parsley before serving.