Butternut Squash Gratin

Tender, melt-in-your-mouth squash slices are layered with cheese, garlic thyme olive oil sauce, and walnut brown sugar crumble. This elegant vegetarian side dish is fantastic for Thanksgiving and the holidays!

Course Side Dish

Cuisine American

Prep Time 30

Cook Time 1

Total Time 1 30

Servings ½-cup servings

Calories 345kcal

Author Lizzie Streit, MS, RDN

Equipment

12-inch cast iron skillet or round or oval baking dish (see notes)

Ingredients

1.5 pounds butternut squash about 1 small squash
6 tablespoons extra virgin olive oil divided
2 large shallots diced, about 1 cup
4 cloves garlic minced
2 tablespoons fresh thyme leaves
2 tablespoons salted butter
¾ cup vegetable broth divided
½ teaspoon freshly ground black pepper
¼ teaspoon salt
1 cup roughly chopped walnuts
2 tablespoons light brown sugar
½ teaspoon ground nutmeg
3 ounces gruyere cheese freshly grated, about 1 and ¼ cup
2 ounces parmesan cheese freshly grated, about ¾ cup

US Customary - Metric

Instructions

Preheat the oven to 400℉/207℃. Grease a 12-inch cast iron skillet or 11- to 12-inch oval or round baking dish with butter and set aside.
Peel and trim the butternut squash. Slice the squash in half where the top meets the base. Cut the base in half lengthwise and scoop out the seeds. Use a mandoline or very sharp knife to slice the squash pieces into thin disks. If you are using a knife, make sure the disks are ⅛-inch thick or thinner.
The slices from the top portion of the squash will be perfect circles, but the slices from the halved base will be half-circles. You can tuck the half-circles into the bottom layers of the gratin and use the full circles where they'll be visible on top if desired.
Prepare the gratin sauce. Warm 2 tablespoons of the olive oil in a medium skillet over medium heat. Add the diced shallots and cook for a few minutes until lightly browned. Add the garlic and cook for a minute until fragrant. Stir in the rest of the olive oil, thyme, butter, ½ cup of vegetable broth, pepper, and salt. Cook until the butter is melted. Remove from heat.
In a small bowl, stir together the chopped walnuts, brown sugar, and nutmeg. Prepare the grated cheeses.
Layer the gratin. First, pour the the remaining ¼ cup of broth into the bottom of the greased pan. Next, make a layer of butternut squash slices by overlapping them like shingles. Drizzle about ⅓ of the olive oil sauce over the first layer of squash. Sprinkle ⅓ of the walnut brown sugar mixture on top, followed by ⅓ of each the gruyere and parmesan cheeses.
Repeat the process two times, each with another layer of squash, ⅓ of the olive oil sauce, ⅓ of the walnut brown sugar mixture, and ⅓ of the cheeses.
Cover the pan tightly with aluminum foil. Place it on the center rack of the preheated oven. Cook for 35 to 45 minutes until the squash is tender and browned around the edges and the cheese is melted. Remove the foil and bake for another 5 to 10 minutes until browned to your liking (if you want it more browned; this step is optional). Be careful not to cook it for too long with the foil removed so that the walnuts don't burn.
Scoop onto dishes and enjoy!
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Notes

Equipment note: This dish looks beautiful in a round or oval dish, like a cast iron skillet or oval casserole dish. If you choose to use a cast iron, please note that the bottom layer and edges of the gratin will turn a dark brown color as they caramelize in the oven, partially due to the reaction of the shallot and garlic sauce with the iron pan. This is harmless and fine to eat, but if you don't want the dark brown color on the bottom, you can bake the gratin in a dish that isn't cast iron.
Make ahead: You can layer the gratin and bake it at a later time by following the steps up until putting it in the oven. Cover tightly with foil and keep in the refrigerator for up to 12 hours, then bake when you are ready. Alternatively, you can bake the dish and reheat it at a later time. Keep it covered with foil in the refrigerator for up to 6 hours, then reheat covered in the oven for 10 to 15 minutes at 350 degrees F/176 degrees C. Keep a close eye on it so the walnuts don't overcook/burn.
Leftovers: Store leftovers in an airtight container in the refrigerator for 2 to 3 days. Reheat in the microwave in 30-second intervals on high until warmed through.

Nutrition