This Butternut Squash Gratin with Caramelized Onions & Gruyere is a dish to remember! Tender butternut squash, sweet caramelized onions, sage-infused cream, and nutty gruyere cheese make this one very special. It is the side dish of all side dishes – perfect for the holiday season!
When it comes to Thanksgiving dinner (or any dinner really), I think the sides play just as big of a role as the main protein.
I am definitely the one who fills my plate with one serving of turkey and goes back for seconds of all the sides.
This Butternut Squash Gratin with Caramelized Onions & Gruyere is just the sort of side dish I go back for time and time again.
It’s rich and decadent, creamy and satisfying, and a little bit unexpected. A fun and new way to have your gratin – no potatoes in sight.
And while I love potatoes more than most foods, this potato-less gratin right here is perfection.
This gratin is not a low maintenance dish, but I think the same can be said for most gratin dishes out there. You have to caramelize onions, break down a butternut squash, grate cheese, and then assemble everything.
I know, I know. Not exactly simple. But the results are SO worth it! AND you can prep it entirely ahead of time. On a busy day like Thanksgiving, this is exactly the sort of dish I try to do ahead.
Ingredients You Need to Make This Butternut Squash Gratin:
For the Caramelized Onions:
- Butter
- Fresh sage
- Yellow onions, thinly sliced
- Light brown sugar
- Pinch of salt
For the Gratin:
- Heavy cream
- Fresh sage
- Nutmeg
- Salt and pepper
- Butternut squash — peeled and cut into thin slices (I used a 3-lb squash)
- Gruyere cheese
- Parmesan cheese
- Panko breadcrumbs
How to Make This Butternut Squash Gratin:
For the Caramelized Onions:
- Add the butter to a skillet and set over medium heat. Add the sage leaves and cook for a few minutes or until they are crisp. Remove the sage leaves and set aside – we will use these as garnish later.
- Add the sliced onions, sugar, and salt and cook, stirring every few minutes, for 25-30 minutes, or until the onions are softened and lightly caramelized. Be patient – this can take some time (and can also be done ahead of time).
For the Gratin:
- Preheat the oven to 375°F and grease a large round baking dish (10-12 inches in diameter).
- In a measuring cup or bowl, whisk together the cream, sage, nutmeg, salt, and pepper. Pour a couple tablespoons of the cream over the bottom of the greased baking dish.
- Add a layer of the butternut squash slices. Add roughly a third of the caramelized onions. Sprinkle over roughly ⅓ of the grated gruyere cheese. Pour over roughly ⅓ of the cream mixture.
- Continue layering two more times: squash, onions, cheese, cream.
- Sprinkle the grated parmesan cheese and panko breadcrumbs over the top layer. Cover the pan loosely with tin foil and then place the pan on a baking sheet.
- Bake for 50-60 minutes or until a sharp knife goes through the squash easily. Remove the foil and bake for another 10-15 minutes or until the top is golden and the gratin is bubbly around the edges.
- Allow to cool for 15 minutes before serving. Just before serving, garnish with the reserved crispy sage leaves.
Other Recipes You Might Enjoy:
- Warm Butternut Squash Ricotta Dip with Spiced Sage Butter
- Thai Butternut Squash Dip
- Butternut Squash, Sage, & Goat Cheese Lasagna
- Cheesy Mashed Potato Gratin with Sage Butter
- Roasted Garlic & Gouda Potato Gratin
This gratin is everything the holidays should be: special.
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Butternut Squash Gratin with Caramelized Onions & Gruyere
- Total Time: 2 hours
- Yield: 8 servings 1x
Description
This Butternut Squash Gratin with Caramelized Onions & Gruyere is a dish to remember! Tender butternut squash, sweet caramelized onions, sage-infused cream, and nutty gruyere cheese make this one very special. It is the side dish of all side dishes – perfect for the holiday season!
Ingredients
For the Onions:
- 2 tablespoons butter
- 8 large sage leaves
- 2 large yellow onions, thinly sliced
- 1 tablespoon light brown sugar
- Pinch of salt
For the Gratin:
- 1 1/4 cups heavy cream
- 1/4 cup chopped fresh sage (roughly 2-3 whole sage leaves)
- 1/2 teaspoon ground nutmeg
- 1 teaspoon kosher salt
- 1/2 teaspoon ground black pepper
- 1 large butternut squash, peeled and cut into thin slices (I used a 3-lb squash)
- 6 oz grated gruyere cheese
- 2 oz grated parmesan cheese
- 1 cup panko breadcrumbs
Instructions
For the Onions:
- Add the butter to a skillet and set over medium heat. Add the sage leaves and cook for a few minutes or until they are crisp. Remove the sage leaves and set aside – we will use these as garnish later.
- Add the sliced onions, sugar, and salt and cook, stirring every few minutes, for 25-30 minutes, or until the onions are softened and lightly caramelized. Be patient – this can take some time (and can also be done ahead of time).
For the Gratin:
- Preheat the oven to 375°F and grease a large round baking dish (10-12 inches in diameter).
- In a measuring cup or bowl, whisk together the cream, sage, nutmeg, salt, and pepper. Pour a couple tablespoons of the cream over the bottom of the greased baking dish.
- Add a layer of the butternut squash slices. Add roughly a third of the caramelized onions. Sprinkle over roughly ⅓ of the grated gruyere cheese. Pour over roughly ⅓ of the cream mixture.
- Continue layering two more times: squash, onions, cheese, cream.
- Sprinkle the grated parmesan cheese and panko breadcrumbs over the top layer. Cover the pan loosely with tin foil and then place the pan on a baking sheet.
- Bake for 50-60 minutes or until a sharp knife goes through the squash easily. Remove the foil and bake for another 10-15 minutes or until the top is golden and the gratin is bubbly around the edges.
- Allow to cool for 15 minutes before serving. Just before serving, garnish with the reserved crispy sage leaves.
Notes
To make this ahead, I recommend prepping and assembling the gratin in its entirety – except for the breadcrumb topping. Cover and refrigerate the baking dish until you are ready to bake it. Allow it to come to room temperature before baking and add the breadcrumbs just before you put it in the oven.
- Prep Time: 15 minutes
- Cook Time: 1 hour 45 minutes
- Category: side dishes
Keywords: butternut squash gratin, butternut squash and gruyere gratin, butternut squash and caramelized onion gratin, holiday side dishes, thanksgiving side dishes, butternut squash side dishes
Hi There. I'm Molly. I'm a food-obsessed, self-taught cook and I can't wait to share my passion for all things culinary with you. My love for egg yolks is just the tip of the iceberg!
really like gruyere and onion paring, and works well as a gratin too, so thank you!