Creating Cheesy Butternut Squash Casserole is simple. Follow these steps for a delicious outcome:

1. Preheat Oven: Preheat your oven to 375°F (190°C) and grease a 9×13-inch baking dish.
2. Prepare Squash: Peel and dice the butternut squash into small cubes for even cooking.
3. Boil Squash: In a large pot, bring water to a boil. Add the diced squash and cook for about 10 minutes until tender. Drain and set aside.
4. Mix Cheeses: In a large mixing bowl, combine cheddar, mozzarella, and Parmesan cheese. Reserve a bit of cheese for topping.
5. Combine Ingredients: In another bowl, whisk together heavy cream, eggs, garlic powder, onion powder, salt, black pepper, and nutmeg. Mix well.
6. Combine Squash and Cheese Mixture: Add the cooked butternut squash to the cheese mixture, followed by the cream mixture. Stir until everything is well combined.
7. Transfer to Baking Dish: Pour the mixture into the prepared baking dish, spreading it evenly.
8. Add Topping: If desired, sprinkle breadcrumbs on top and drizzle with olive oil for a crispy texture.
9. Bake: Place the casserole in the preheated oven and bake for 30-35 minutes, or until golden and bubbly.
10. Cool and Serve: Allow the casserole to cool for a few minutes before serving to let the flavors meld.

These steps will guide you in creating this incredible casserole effortlessly.