Butternut Squash Gratin

1 tablespoon butter

1 tablespoon olive oil

2 large onions, cut into 1-inch squares

3 tablespoons chopped fresh sage

salt and freshly ground black pepper to taste

3 pounds butternut squash - peeled, seeded, and cut into 1/2-inch cubes

2 cloves garlic, minced

¾ teaspoon salt

10 tablespoons heavy whipping cream

1 cup fresh bread crumbs

1 ½ tablespoons butter, melted

Preheat oven to 350 degrees F (175 degrees C). Grease a gratin baking dish with butter.

Heat 1 tablespoon butter and olive oil in a large skillet over low heat; add onions and sage. Cover and cook, stirring occasionally, until onions are browned, about 25 minutes. Season with salt and black pepper.

Place a steamer insert into a saucepan and fill with water to just below the bottom of the steamer. Bring water to a boil. Add squash, cover, and steam until tender, 10 to 20 minutes. Transfer squash to prepared gratin dish; toss with garlic and 3/4 teaspoon salt. Add the caramelized onions to the pan and gently mix to combine.

Warm cream in a saucepan over low heat; pour over squash mixture. Stir to coat. Combine bread crumbs and 1 1/2 tablespoons melted butter together in a bowl; sprinkle over squash mixture.

Bake in the preheated oven until gratin is bubbling and breadcrumbs are browned, 20 to 25 minutes.