Heat olive oil in a large skillet over medium heat. Add the onions, green bell peppers, and optional mushrooms, and cook until softened, about 8-10 minutes. Stir in the minced garlic and cook for an additional minute, then set the mixture aside.

Increase the heat of the skillet to medium-high. Add the sliced ribeye steak in batches and sear for 1-2 minutes on each side until browned. Chop the steak into smaller pieces while it's cooking, then set aside.

Return the sautéed vegetable mixture to the skillet with the steak. Stir in Worcestershire sauce, garlic powder, onion powder, salt, black pepper, and if desired, red pepper flakes. Cook together for an additional 2-3 minutes until everything is well combined.

In a separate saucepan, melt the butter over medium heat. Whisk in the flour to create a roux, cooking for 1-2 minutes. Gradually whisk in the milk until the mixture is smooth and creamy. Continue to simmer for 5-7 minutes until thickened, then stir in both shredded cheeses until melted. Season with nutmeg if using.

Bring a large pot of salted water to a boil. Cook the fresh cheese tortellini according to package directions, which usually takes about 3-5 minutes. Drain and set aside.

Gently toss the cooked tortellini with the cheesesteak filling. Pour the creamy cheese sauce over the top, mixing delicately until everything is beautifully coated.

Dish out the Cheesesteak Tortellini onto plates or in bowls, then garnish with freshly chopped parsley and grated Parmesan cheese. For those who enjoy a kick, add a dash of hot sauce!