Butternut squash au gratin is the cheesy delicious side dish your holiday table is missing! This perfect Fall recipe features velvety butternut squash baked in a gruyere cream sauce and topped with golden, buttery breadcrumbs. YES PLEASE!
This unique side dish is the perfect addition to your Thanksgiving and Christmas feasts! Or, serve it anytime to be instantly transported to cozy holiday memories. We love it as an indulgent dish alongside our Herbs de Provence Roast Chicken or our Cider Braised Chicken Thighs!
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Ingredients
Butternut squash au gratin is a casserole made from slices of butternut squash baked in a gruyere version of our Cheese Fondue Sauce recipe! Then, it’s topped with buttery thyme breadcrumbs and more cheese. So good! Here’s what you’ll need:
- Gruyere Cheese - The natural sweet flavors of butternut squash pair perfectly with the nutty flavors of gruyere. Comté, Jarlsburg and Emmental can make for fine substitutes.
How To Make This Recipe
This side dish is easy to make and can be assembled ahead of time and baked just in time for dinner!
1. Start by peeling, deseeding and slicing your butternut squash. Slice the squash into bite-sized pieces about ⅛ - ¼ of an inch thick. Then, slice a quarter of a yellow onion very thinly. Set aside in a large bowl.
2. To make the gruyere cheese sauce, start by making a roux. In a medium sauce pot, melt butter and whisk in equal parts of flour until a paste forms.
3. Whisk in milk, a little at a time. Whisk in salt, pepper, nutmeg and a little cinnamon. Bring to a simmer and cook for 5 - 10 minutes, stirring frequently, until thick enough to coat the back of a spoon.
4. Whisk in small handfuls of shredded cheese. Cook, while whisking, until cheese is completely melted and sauce is velvety smooth. Do not boil.
5. Toss the squash and onion in the gruyere cheese sauce until each piece is coated. Then, transfer the mixture into a greased casserole dish and cover with foil. You can bake the butternut squash au gratin immediately, or chill in the refrigerator for a day or two, until ready to bake. (If you refrigerate the dish for later, bring the au gratin to room temperature and/or allow additional baking time. More on this below.)
6. Bake the covered au gratin in a preheated oven for 20 minutes. Meanwhile, prepare the breadcrumb topping. In a medium mixing bowl combine the breadcrumbs, melted butter, thyme, seasoning and shredded gruyere cheese. Toss well to combine.
7. Uncover the au gratin and sprinkle the topping over it. Bake for 20 - 25 additional minutes or until the squash is easily pierced with a paring knife, the topping is golden brown and the cheese sauce is bubbling around the edges!
Allow the dish to rest for 10, or so, minutes to slightly cool and set. Slice (or scoop!), serve and enjoy!!
Instructions for Making Ahead & Reheating
Butternut squash au gratin is a great dish for the holidays and potluck dinners because it can be made a day or two ahead of time and reheated when ready to serve.
- Fully prepare this recipe according to the instructions below. Keep covered in the refrigerator for 1 - 2 days until ready to eat.
- A few hours before dinner time, remove this casserole from the refrigerator and allow it to temper at room temperature. (You can technically bake it from cold, but it will require much more time in the oven and bake unevenly).
- Cover with foil and bake for 20 - 30 minutes or until the center of the Butternut Squash au Gratin reaches 155° Fahrenheit on an instant read thermometer. (We use this one from ThermoWorks.)
- If desired, remove the foil and allow the breadcrumb topping to crisp for an additional 5, or so, minutes.
- Allow the dish to slightly cool and set before slicing and serving. Enjoy!
Saving The Leftovers
Leftovers are one of my favorite holiday perks! If you have any leftover butternut squash au gratin, it can be saved and kept covered in the refrigerator for 3 - 5 days.
Reheat in the oven (using the instructions above and adjusting the time down for smaller portions) or in a microwave to an internal temperature of 155° Fahrenheit.
More Holiday Side Dishes To Love!
Check out these other yummy side dishes to round out your holiday meals!
If you make this recipe, please leave us a star rating below!
Recipe
Butternut Squash au Gratin
Special Equipment
- 2 quart baking dish - This fits perfectly in a standard 8 x 8 inch pyrex dish.
- Instant Read Thermometer Recommended for reheating
Ingredients
Butternut Squash au Gratin
- 1 medium butternut squash about 2 pounds; peeled, seeded and sliced into bite-sized pieces ⅛ - ¼ inch thick
- ¼ medium yellow onion peeled and thinly sliced
- 1 recipe Gruyere Cheese Sauce below
- 1 recipe Breadcrumb Topping below
Gruyere Cheese Sauce
- 2 Tablespoons butter
- 2 Tablespoons all-purpose flour
- 1 ¼ Cups whole milk cold or room temperature
- 4 ounces gruyere cheese shredded
- 1 Tablespoon fine kosher salt*
- 1 teaspoon ground white pepper OR freshly-ground black pepper
- ½ teaspoon nutmeg freshly ground
- ¼ teaspoon ground cinnamon
Breadcrumb Topping
- ⅔ Cup panko breadcrumbs
- 1 ounce gruyere cheese shredded
- 2 teaspoons fresh thyme leaves chopped
- 1 Tablespoon butter softened or melted
Instructions
Butternut Squash au Gratin
- Arrange a rack in the center third of the oven and preheat to 375° Fahrenheit (190° celsius). Prepare a 8 x 8 inch baking dish with non-stick cooking spray or butter. Set aside.
- Combine sliced squash and onion on a large mixing bowl. Set aside while you prepare the Gruyere Cheese Sauce.
Gruyere Cheese Sauce
- In a medium sauce pan, melt butter over medium heat. Whisk in flour and cook for 1 - 2 minutes. Add in milk, a little at a time while whisking constantly. Bring to a simmer, stirring often, and cook gently for 5 - 10 minutes until the sauce has reduced slightly and is beginning to thicken. If there are any lumps, strain through a fine mesh strainer and return to a cleaned pot.
- Lower heat to it's lowest setting. Add shredded gruyere cheese, a little at a time, while stirring. Once cheese is completely melted and the sauce is velvety smooth, remove from heat and season with salt, pepper, nutmeg and cinnamon.
- Pour the gruyere cheese sauce over the squash and onion. Toss until each piece of squash is coated in sauce. Transfer to the prepared baking dish. Tap or shake the dish on the counter to help level the squash and avoid air bubbles. Cover with foil and bake for 20 minutes. Meanwhile, prepare the Breadcrumb Topping.
Breadcrumb Topping
- In a small mixing bowl, combine breadcrumbs, shredded cheese, thyme and butter. Mix until well combined.
- After 20 minutes of baking, remove the Butternut Squash au Gratin for the oven and remove the foil. Sprinkle the breadcrumb topping over the squash and continue baking for an additional 20 - 25 minutes or until the squash is tender, cheese is bubbly and topping is golden brown.
- Allow the Butternut Squash au Gratin to slightly cool and set for 10 minutes before slicing and serving. Enjoy!
*Unless otherwise noted, foodworthfeed recipes are developed using Diamond Crystal brand kosher salt. If using iodized or table salt, reduce quantities by about half.
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