1. Sauté the vegetables: Heat olive oil in a skillet over medium heat. Add onions, bell peppers, and mushrooms (if using). Cook until softened.
2. Cook the steak: Push vegetables to one side of the skillet. Add steak and cook to desired doneness, breaking it into smaller pieces.
3. Combine filling: Mix steak and vegetables. Top with provolone cheese, cover, and reduce heat to melt the cheese. Stir to combine.
4. Make the roux: In a saucepan, melt butter over medium heat. Whisk in flour and cook for 1-2 minutes.
5. Add liquids: Slowly whisk in heavy cream and milk until the sauce thickens.
6. Incorporate cheese and seasonings: Reduce heat to low. Stir in Parmesan cheese, salt, pepper, and Italian seasoning until melted and smooth.
7. Cook tortellini: Boil tortellini according to package directions until al dente. Drain.
8. Combine everything: Gently mix the cheesesteak filling, parmesan sauce, and cooked tortellini in a large bowl. Adjust sauce consistency with pasta water if needed.
9. Serve immediately.