Bring a large pot of salted water to a boil over high heat. Add the cheese tortellini and cook according to package instructions, typically around 3-5 minutes for fresh or 8-10 minutes for frozen. Drain and keep warm.

In a large skillet, heat olive oil over medium-high heat. Add sliced beef sirloin, season with salt and pepper, and cook for about 5 minutes until browned. Remove from skillet.

In the same skillet, add diced green bell pepper and chopped onion, sauté for about 5-7 minutes until softened. Stir in minced garlic and cook for additional 1-2 minutes.

In a separate saucepan, melt butter over medium heat. Whisk in flour and cook for about 1 minute until it forms a light roux.

Gradually pour in whole milk while whisking to prevent lumps. Continue stirring for about 3-4 minutes until thickened.

Reduce heat to low and add shredded provolone cheese and grated Parmesan cheese, stirring until melted and smooth. Season to taste.

Return the cooked tortellini, sautéed beef, and vegetables to the saucepan and stir gently. Cook for an additional 2 minutes on low heat.

Transfer to a serving dish, garnish with parsley or extra Parmesan if desired, and serve warm.