Cook Tortellini: Bring a large pot of salted water to a boil. Add cheese tortellini and cook according to package instructions, usually around 3-5 minutes, until they float and are tender but firm. Drain and set aside.

Sauté Beef: In a large skillet, heat olive oil over medium-high heat. Add beef sirloin and cook for about 5 minutes until browned. Remove from skillet, leaving the juices.

Sauté Vegetables: In the same skillet, add more olive oil if needed and sauté green bell pepper and onion over medium heat for 5-7 minutes. Add minced garlic and cook for an additional minute until fragrant. Remove from heat.

Prepare Sauce: In a separate saucepan, melt butter. Whisk in flour and cook for 1 minute. Gradually add whole milk, whisking until the sauce thickens, about 3-4 minutes.

Add Cheese: Stir in provolone and Parmesan cheeses until melted and smooth. Season with salt and pepper to taste.

Combine: Add cooked tortellini, sautéed beef, and vegetables to the sauce, folding gently to coat. Heat on low for 1 minute to meld the flavors.

Serve: Transfer to a serving dish, garnishing with parsley or extra Parmesan cheese if desired. Enjoy your comforting dish!