Creating this Butternut Squash Casserole involves straightforward steps to achieve a delicious result:

1. Preheat Oven: Preheat your oven to 375°F (190°C).
2. Prepare Squash: In a large pot, bring salted water to a boil. Add the diced butternut squash and cook for about 10 minutes or until tender. Drain and set aside.
3. Sauté Onions and Garlic: In a skillet, heat olive oil over medium heat. Add diced onions and sauté until translucent, about 5-7 minutes. Stir in minced garlic and cook for an additional minute.
4. Combine Ingredients: In a large mixing bowl, combine the cooked butternut squash, sautéed onions and garlic, chicken or vegetable broth, heavy cream, thyme, nutmeg, salt, and black pepper. Mix until well combined.
5. Transfer to Baking Dish: Pour the mixture into a greased casserole dish, spreading it evenly.
6. Prepare Topping: In a separate bowl, mix breadcrumbs with grated Parmesan cheese. Sprinkle this mixture evenly over the casserole.
7. Bake: Place the casserole in the preheated oven and bake for 30-35 minutes until the top is golden brown and crispy.
8. Cool Slightly: Once done, take it out of the oven and let the casserole cool for about 15-20 minutes before serving.

By following these steps, you can create a wonderful Butternut Squash Casserole that will surely impress your family and friends!