Beef Tetrazzini Casserole

1. Preheat your oven to 350°F (175°C).

2. Cook the egg noodles according to the package instructions. Drain and set aside.

3. In a large skillet, heat the olive oil over medium-high heat. Add the sliced beef and cook until browned. Remove the beef from the skillet and set aside.

4. In the same skillet, add the butter and sauté the onions and garlic until translucent.

5. Add the mushrooms and continue to cook until they are tender and browned, about 5 minutes.

6. Sprinkle the flour over the vegetables and stir well to combine. Cook for another minute to eliminate the raw flour taste.

7. Gradually pour in the beef broth, stirring constantly until the mixture thickens.

8. Reduce the heat to low and stir in the heavy cream, sour cream, and half of the Parmesan cheese. Season with salt and pepper to taste.

9. Return the beef to the skillet, combine with the sauce, and simmer for a few minutes until everything is well coated.

10. In a large mixing bowl, combine the cooked noodles with the beef and sauce mixture.

11. Transfer the mixture to a greased 9×13 inch baking dish. Sprinkle the top with the remaining Parmesan cheese and mozzarella cheese.

12. Bake in the preheated oven for 25-30 minutes, or until the top is golden brown and bubbly.

13. Garnish with freshly chopped parsley before serving.

For a lighter version, you can substitute the heavy cream with half-and-half or milk, though the sauce will be less rich. Try adding different vegetables like peas, spinach, or bell peppers for added texture and nutrition. If you wish to make it gluten-free, use gluten-free pasta and a suitable thickener such as cornstarch instead of all-purpose flour. For an added crunch, consider topping the casserole with breadcrumbs mixed with a bit of melted butter before baking.