Preheat your oven to 425°F (220°C) with a rack positioned in the upper third of the oven.

Line a large baking sheet with aluminum foil.

Arrange the squash halves on the baking sheet with the cut sides facing upward.

Brush the exposed flesh lightly with oil.

Place the squash in the oven and roast for approximately 40 minutes, or until the flesh is very tender when pierced with a fork.

Remove from the oven and allow the squash to cool for about 10 minutes, or until it can be handled comfortably.

Reduce the oven temperature to 350°F (175°C).

Using a spoon, scoop the roasted squash flesh into a large mixing bowl.

Mash thoroughly with a potato masher or large fork until smooth.

Add the milk, eggs, shallot, garlic, ⅓ cup Parmesan cheese, ½ teaspoon salt, and ¼ teaspoon black pepper.

Stir until all ingredients are evenly combined and the mixture is smooth and creamy.

Lightly grease a 7-by-11-inch baking dish.

Pour the squash mixture into the prepared dish and spread it into an even layer.

In a medium bowl, combine the breadcrumbs, melted butter, parsley, sage, rosemary, the remaining ⅓ cup Parmesan cheese, and the remaining ¼ teaspoon each of salt and black pepper.

Mix until the breadcrumbs are evenly coated and the herbs are distributed throughout.

Sprinkle the breadcrumb mixture evenly over the squash filling.

Place the casserole in the preheated 350°F (175°C) oven.

Bake for 28 to 30 minutes, or until the filling is fully set and heated through.

The edges should be lightly bubbling and the center should no longer appear loose.

Switch the oven to the broil setting.

Place the casserole under the broiler and cook for 1 to 3 minutes, watching carefully.

Broil just until the topping becomes golden brown and crisp.

Do not leave it unattended, as the breadcrumb topping can brown very quickly.

Remove the casserole from the oven and allow it to rest for a few minutes before serving.

Spoon portions onto individual plates and serve warm.

This casserole pairs beautifully with roasted poultry, pork, beef, or as part of a holiday meal.

This butternut squash casserole combines creamy roasted squash with savory Parmesan, garlic, and shallots, all topped with a crisp herb-seasoned breadcrumb crust. The combination of sage, rosemary, and parsley brings classic autumn flavors, while the Parmesan adds richness and depth.

Elegant enough for holiday gatherings yet simple enough for family dinners, this casserole is a comforting and flavorful way to showcase sweet roasted squash.