Bring a large pot of salted water to a boil.
Cook tortellini until just al dente, one minute shy of package time. Drain.
Pat steak dry. Season with 1 pinch salt and pepper.
Heat olive oil in a large skillet over medium-high. Sear steak in two batches.
Transfer browned steak to a plate. Leave drippings in the skillet.
Melt butter in the skillet over medium heat. Add onion, pepper, and mushrooms.
Sauté until vegetables soften and lightly brown, about 6 minutes.
Stir in garlic and Italian seasoning. Cook until fragrant, 30 seconds.
Sprinkle in flour. Stir constantly for 1 minute to form a roux.
Whisk in beef broth and Worcestershire. Simmer until slightly thickened, 2 to 3 minutes.
Pour in half-and-half. Simmer gently until creamy, 2 minutes. Do not boil hard.
Remove from heat. Stir in provolone until melted and smooth.
Return steak and tortellini to the skillet. Toss to coat and warm through.
Season with remaining salt, pepper, and red pepper flakes. Garnish with parsley.
Serve hot with Parmesan on top.