Creating Cheesy Low Carb Philly Cheesesteak Casserole is straightforward if you follow these simple steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C).
2. Sauté the Vegetables: In a large skillet over medium heat, add sliced onions, bell peppers, and mushrooms. Sauté for 5-7 minutes until they begin to soften. Add minced garlic and cook for another minute. Remove the vegetables from the skillet and set aside.
3. Cook the Beef: In the same skillet, add the thinly sliced beef. Cook until browned and fully cooked, about 5-7 minutes. Drain any excess fat if necessary.
4. Combine Ingredients: Return the sautéed vegetables to the skillet with the beef. Add Worcestershire sauce, salt, black pepper, and Italian seasoning. Stir everything together until well combined.
5. Prepare the Cream Mixture: In a mixing bowl, combine heavy cream with half of the shredded cheese and Parmesan cheese. Mix until smooth.
6. Layer the Casserole: In a greased 9×13-inch casserole dish, layer the beef and vegetable mixture evenly, then pour the cream mixture over the top.
7. Top with Cheese: Sprinkle the remaining shredded cheese on top of the casserole.
8. Bake: Place the casserole in the preheated oven and bake for 30-35 minutes or until the cheese is bubbly and golden brown.
9. Garnish and Serve: Allow the casserole to cool for 5-10 minutes before slicing. Garnish with fresh parsley if desired.

Following these steps will lead you to an incredible Cheesy Low Carb Philly Cheesesteak Casserole that will impress everyone at the dinner table.