Bring a large pot of salted water to a boil. Add the cheese tortellini and cook according to package instructions until al dente, approximately 3-5 minutes. Drain and set aside.

Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Add thinly sliced beef sirloin and cook for about 5 minutes, stirring occasionally, until browned. Remove beef and set aside.

In the same skillet, add another tablespoon of olive oil if needed, then toss in sliced green bell pepper and onion. Sauté for 5-7 minutes until softened. Add minced garlic and cook for an additional minute. Remove from heat.

In a separate saucepan, melt 2 tablespoons of butter over medium heat. Whisk in 2 tablespoons of all-purpose flour for about 1 minute to form a roux.

Slowly add 2 cups of whole milk to the roux, whisking constantly to avoid lumps. Cook for 3-4 minutes until thickened.

Stir in 1 cup of shredded provolone cheese and ½ cup of grated Parmesan cheese. Continue stirring until cheeses melt completely and sauce is smooth.

Fold the cooked tortellini, sautéed beef, and vegetable mixture into the cheese sauce until evenly combined.

Serve hot, garnished with parsley or extra Parmesan cheese if desired.