Preheat your oven to 375°F (190°C).

In a large pot, add the cubed butternut squash and cover with water. Boil for about 10-12 minutes until tender. Drain and set aside.

In a skillet, heat 2 tablespoons of olive oil over medium heat. Add the chopped onion and cook until translucent, about 5 minutes. Stir in the minced garlic, cooking for an additional minute.

In a large mixing bowl, mash the cooked butternut squash until smooth. Add the sautéed onions and garlic, Parmesan cheese, salt, pepper, nutmeg, and vegetable broth. Mix until well combined.

Pour the mixture into a greased casserole dish, smoothing it out evenly.

Sprinkle the breadcrumbs generously over the squash mixture.

Place the casserole in the oven and bake for about 25-30 minutes, or until the top is golden brown and crispy.

Remove from the oven, garnish with fresh herbs if desired, and serve warm.