In a large pot or Dutch oven, heat olive oil over medium heat. Add the diced onion and green bell pepper, cooking for about 5 minutes until softened.
Add the minced garlic and sliced beef sirloin to the pot. Cook for an additional 5-7 minutes until the beef is browned and no longer pink.
Stir in the beef broth and bring the mixture to a gentle boil.
Add the cheese tortellini to the pot and reduce the heat to a simmer. Cook according to the tortellini package instructions, usually about 5-7 minutes, until the tortellini are tender.
Once the tortellini is cooked, stir in the milk and shredded provolone cheese. Cook on low heat until the cheese has melted and the sauce is creamy. Season with salt and pepper to taste.
Serve hot, garnished with fresh parsley if desired.
For extra flavor, incorporate mushrooms or different colored bell peppers if you desire.
This dish can be made ahead of time and reheated, but it's best enjoyed fresh to maintain the creaminess of the sauce.