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Cheddar and thyme butternut gratin is a simple, but surprisingly flavorful side dish that pairs well with just about anything. It’s a delicious new way to use winter squash!

front view of roasted butternut squash gratin with cheese

Looking through my side dish recipes, I realized that – like most side dish recipes – a lot of them feed a crowd! Which is of course a good thing most of the time, but it doesn’t hurt to have a few small-batch options on hand for those times when you’re just cooking for you +1.

This butternut gratin is a great holiday or winter side dish because it’s so hearty. Butternut squash is the base and it’s flavored simply with onion and garlic sautéed in butter. Fresh thyme brightens it up, and a hint of nutmeg makes it interesting. Richness comes in the form of cream (or half and half) and sharp cheddar.

Butternut au gratin is equally lovely paired with roast chicken as it is prime rib. It requires minimal hands-on prep so you can spend more time on whatever else you’re serving with it. And it doubles or triples easily if you need to scale it up!

What holiday side dish do you look forward to every year?

overhead view of easy butternut squash gratin with salt and pepper shakers

Ingredients in Butternut Squash Gratin

In this section I explain the ingredients and give substitution ideas. For the full recipe (including ingredient amounts), see the recipe card below.

  • Butter – butter adds a rich base flavor; we use it to sauté the onion and garlic
  • Onion and garlic – this classic duo adds delicious depth of flavor; and if you prefer, you can use 1 leek instead of the onion
  • Fresh thyme – or you can use fresh rosemary instead; if you only have dried thyme leaves on hand, use about 1/4 teaspoon instead of fresh thyme
  • Salt and black pepper – these pantry-staple seasonings make sure our cheesy butternut casserole isn’t bland
  • Nutmeg – we only need a pinch of nutmeg (preferably freshly-grated nutmeg if available) to add another layer of flavor to this dish
  • Cubed butternut squash – butternut is the star of the show; you can use store-bought cubed butternut squash (and roast it yourself), or frozen cubed butternut (and steam it in the microwave), or get a whole butternut squash (and peel, de-seed, and cube it, and then toss it with a drizzle of olive oil and roast it in a preheated 425F oven until tender, about 20 to 30 minutes)
  • Heavy cream – or half and half
  • Sharp cheddar – the sharp bite pairs well with the nutty flavor of butternut

Substitute for Butternut Squash

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For this recipe, you can use any type of winter squash that you can peel, de-seed, and cube! A few other good options are fresh pumpkin, acorn squash, buttercup squash, or hubbard squash. Even sweet potato is a good substitute here!

butternut squash bake

How to Make Butternut Gratin

Step 1: Sauté the Onion and Garlic

Heat the butter in a medium-sized skillet over medium to medium-high heat. Once hot, add the onion and cook until starting to soften, about 3 to 5 minutes, stirring occasionally. Add the garlic and cook 1 minute more, stirring constantly. 

Step 2: Add the Seasonings and Mash it a Little Bit

Turn off the heat and stir in the thyme, salt, pepper, and nutmeg. Stir in the butternut squash and use a fork or potato masher to mash about half of it. Stir it all together.

Step 3: Assemble the Casserole and Bake

Transfer the squash mixture to a 2 cup-capacity gratin dish. Pour the cream or half and half on top and sprinkle on the cheese.

Place the gratin dish on top of a foil-lined baking sheet and bake until bubbling throughout, about 15 minutes in a preheated 425F oven. Broil for a couple minutes to brown the top more.

Serve warm.

Storage and Reheating

You can store leftovers covered in the fridge for up to 4 days. This butternut casserole reheats well in the oven; to do so, cover it with foil and bake in a preheated 350F oven until warm throughout.

cheesy butternut squash casserole

Butternut Squash Gratin FAQs

Do You Have to Peel Butternut?

Yes, it’s best to peel butternut squash (unless a recipe specifically says not to) because the peel on this winter squash is tough.

How Do You Steam Frozen Butternut Squash Cubes in the Microwave?

Frozen butternut squash cubes are definitely a time-saving option. And you can steam them with minimal effort in the microwave.

Here’s how to steam frozen butternut cubes in the microwave:

  1. Put the frozen squash cubes into a microwave-safe bowl.
  2. Put a slightly damp paper towel on the top.
  3. Microwave on high for 5 minutes, then use potholders to remove the bowl and stir the squash.
  4. Put the damp paper towel back on top, and continue microwaving in 2-minute increments until the squash is tender and warm throughout, stirring between each 2-minute interval.

How Do You Roast Butternut Squash Cubes?

For this recipe I prefer the flavor of roasted butternut squash over steamed squash; I find that roasting adds another dimension of complexity.

It’s easy to roast raw butternut squash cubes:

  1. You can either peel, de-seed, and chop a whole butternut squash or buy it pre-cubed at the grocery store.
  2. Preheat the oven to 425F. Toss the squash with a drizzle of olive oil, and spread it out onto a baking tray.
  3. Roast until the squash is tender, about 20 to 30 minutes, tossing once halfway through.

What Do You Serve with Butternut au Gratin?

With a flavor profile similar to mac and cheese (but better!), this cheesy side dish pairs well with just about anything! Here are a few ideas:

More Butternut Squash Side Dishes to Try

close up front view of butternut squash gratin with thyme

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Cheddar and Thyme Butternut Gratin Recipe

Prep Time10 minutes
Cook Time20 minutes
Servings: 2 servings
Cheddar and thyme butternut gratin is a simple, but surprisingly flavorful side dish that pairs well with just about anything. It's a delicious new way to use winter squash!

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Ingredients
 

  • 2 tablespoons unsalted butter
  • 1 small onion diced
  • 1 large clove garlic minced
  • 1 teaspoon minced fresh thyme
  • 1/4 teaspoon salt
  • 1/8 teaspoon black pepper
  • 1 pinch freshly-grated nutmeg
  • 2 cups cubed and cooked butternut squash see Notes
  • 1/4 cup heavy cream or half and half
  • 2 ounces sharp cheddar shredded

Instructions
 

  • Preheat the oven to 425F.
  • Heat the butter in a medium-sized skillet over medium to medium-high heat. Once hot, add the onion and cook until starting to soften, about 3 to 5 minutes, stirring occasionally. Add the garlic and cook 1 minute more, stirring constantly.
  • Turn off the heat and stir in the thyme, salt, pepper, and nutmeg. Stir in the butternut squash and use a fork or potato masher to mash about half of it. Stir it all together.
  • Transfer the squash mixture to a 2 cup-capacity gratin dish. Pour the cream or half and half on top and sprinkle on the cheese.
  • Place the gratin dish on top of a foil-lined baking sheet and bake until bubbling throughout, about 15 minutes. Broil for a couple minutes to brown the top more.
  • Serve warm.

Notes

  • What Kind of Butternut to Use: For this recipe, you can use store-bought cubed butternut squash (and roast it yourself), or frozen cubed butternut (and steam it in the microwave), or get a whole butternut squash (and peel, de-seed, and cube it, and then toss it with a drizzle of olive oil and roast it in a preheated 425F oven until tender, about 20 to 30 minutes). Or you can use leftover roasted butternut squash cubes if you have them on hand!
  • Storage: You can store leftovers covered in the fridge for up to 4 days.
  • Reheating: This butternut casserole reheats well in the oven; to do so, cover it with foil and bake in a preheated 350F oven until warm throughout.

Nutrition

Calories: 408kcal | Carbohydrates: 24g | Protein: 10g | Fat: 32g | Saturated Fat: 20g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 8g | Trans Fat: 0.5g | Cholesterol: 92mg | Sodium: 494mg | Potassium: 642mg | Fiber: 4g | Sugar: 7g | Vitamin A: 16003IU | Vitamin C: 36mg | Calcium: 312mg | Iron: 1mg

Nutritional information is automatically calculated and should be used as an approximate.

Course: Side Dish
Cuisine: American
Keyword: Butternut au Gratin, Butternut Casserole, Butternut Gratin, Butternut Gratin Recipe, Butternut Squash au Gratin, Butternut Squash Bake, Butternut Squash Casserole, Butternut Squash Gratin, Butternut Squash Gratin Recipe

Share it with me on Instagram and leave a comment to let me know your thoughts!

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This post was first published on An Edible Mosaic on December 22, 2017. I updated it with more information on November 19, 2023.

Faith, author of An Edible Mosaic.
About Faith

I’m the writer, recipe developer, photographer, and food stylist behind this blog. I love finding the human connection through something we all do every day: eat! Food is a common ground that we can all relate to, and our tables tell a story. It’s my goal to inspire you to get in the kitchen, try something new, and find a favorite you didn’t know you had.

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4 Comments

  1. How would this reheat if made the day before Thanksgiving?

    1. Branny, This reheats really well! To reheat, I cover it with foil and pop it into a 375F oven until it’s warm throughout.

  2. I’m just starting to cook with butternut squash. I find it very sweet so I love the addition of cheddar and thyme in your recipe. It looks amazing!

  3. Here’s wishing you a merry Xmas — I do love thyme in everything and this looks DIVINE!

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