Follow these simple steps to prepare your Thanksgiving Cheesy Butternut Squash Casserole and delight everyone at your Thanksgiving gathering:

1. Preheat Oven: Preheat your oven to 375°F (190°C).
2. Prepare the Squash: Peel and dice the butternut squash into small cubes. This will allow for even cooking.
3. Boil Squash: Place the diced squash in a pot with enough water to cover it. Bring it to a boil and cook for about 10 minutes or until fork-tender. Drain and set aside.
4. Mix Cheese Sauce: In a large bowl, combine the heavy cream, garlic powder, onion powder, salt, pepper, and nutmeg. Mix in the cheddar and mozzarella cheeses until well blended.
5. Combine Squash and Sauce: Add the cooked butternut squash to the cheese mixture, stirring gently to coat the squash evenly.
6. Transfer to Baking Dish: Pour the mixture into a greased 9×13-inch baking dish, spreading it evenly.
7. Prepare Topping (Optional): If using breadcrumbs, mix them with the grated Parmesan cheese. Sprinkle this mixture over the top of the casserole.
8. Bake: Place the casserole in the preheated oven and bake for 45-50 minutes, or until the top is golden brown and bubbly.
9. Cool Slightly: Once baked, remove the casserole from the oven and let it cool for about 10 minutes.
10. Garnish: Before serving, sprinkle with fresh parsley for a lovely finishing touch.

Following these clear steps will help you create an incredible Thanksgiving Cheesy Butternut Squash Casserole that everyone will rave about!