This acorn and butternut squash gratin casserole has become a go-to side dish in my fall and holiday kitchen. It’s warm, cheesy, and incredibly comforting—like your favorite mashed potatoes, but with deeper flavor and a golden, bubbling top that steals the show. I load it up with creamy mashed squash, tender potatoes, sweet roasted garlic, and a generous blanket of Gruyere cheese. Trust me, it’s the kind of dish that gets scraped clean at the table.
A Little Backstory: How This Casserole Made It to My Table
I first came across a version of this dish in a classic cookbook a few winters ago. It was one of those slow Sunday mornings when I was flipping through recipes, coffee in hand, and the idea of a Provencal-style squash casserole caught my eye. It called for a French pumpkin I’d never even seen at our markets, so I swapped in a mix of acorn and butternut squash, and honestly, I’ve never looked back.
The original recipe was lovely, but I’ve adjusted it over the years to make it even more flavorful and practical. Roasting garlic until buttery soft, layering in sautéed onions, adding a splash of milk for creaminess, and topping it all with nutty Gruyere—it’s now a staple during the colder months. My family asks for it by name, especially around Thanksgiving.
What Makes This Squash Gratin Special
What I really love about this dish is the texture. It’s not a silky purée, and it’s definitely not a chunky roast. It lands somewhere in between, thanks to the roughly mashed squash and parboiled potatoes. You get bites that are soft and creamy, with just enough texture to keep things interesting.
And that roasted garlic… don’t skip it. When you roast a whole head of garlic, it turns mellow and sweet, almost caramel-like. It melts into the squash and adds this beautiful depth of flavor that makes you go back for seconds (and thirds).
Ingredients You’ll Need
Here’s everything I use to make this cozy gratin. Most of these are pantry staples or easy to find:
- Acorn squash (whole or pre-cut)
- Butternut squash (I prefer pre-cut for this, saves time)
- Russet or yellow potatoes
- Whole garlic head (we’ll roast it until golden and soft)
- Sweet onion
- Dried thyme
- Milk (whole milk gives the best richness)
- Gruyere cheese (adds that irresistible nutty crust)
- Salt, pepper, and freshly grated nutmeg
Tip: If you don’t have Gruyere, go for Swiss or even a mix of mozzarella and parmesan. But if you can get your hands on Gruyere, it’s worth it.
Step-by-Step: How I Make It at Home
Here’s how I usually go about it in my kitchen, especially when I’m prepping ahead for a big meal:
1. Roast the garlic:
I chop off the top of the garlic head, drizzle with olive oil, season it, wrap it in foil, and roast it at 400°F for about 40 minutes. The smell alone makes the house feel cozy.
2. Prep the squash:
If you’re using whole squash, pop it in the microwave for a couple of minutes—it softens just enough to make peeling and cutting way easier. Then I cube it and simmer until fork-tender, about 20 minutes.
3. Boil the potatoes:
Slice the potatoes and cook them just until tender. You want them soft but not falling apart.
4. Sauté the onions:
In a skillet with a bit of olive oil, I cook the onions with thyme until they’re golden and soft. Then I squeeze the roasted garlic into the pan and mash it all together.
5. Mash the squash:
Once the squash is drained, I mash it roughly. You’re not going for smooth here—think rustic.
6. Mix everything:
Into the bowl goes the mashed squash, garlic-onion mixture, boiled potatoes, salt, pepper, and a dash of fresh nutmeg. Give it all a gentle stir and taste to adjust seasoning.
7. Assemble:
I pour the whole mix into a greased 9×13″ baking dish, drizzle milk over it, and top it with a thick layer of shredded Gruyere.
8. Bake:
Into the oven it goes at 400°F until the top is golden and bubbling, about 30 minutes. Let it cool slightly before serving.
Serving Ideas from My Kitchen
If you’re making this for the holidays, it pairs beautifully with roasted turkey, glazed ham, or even a slow-cooked pork loin. That savory-sweet flavor goes so well with richer mains.
For everyday meals, I like serving it alongside simple roasted chicken or grilled sausages. It also holds up well on its own if you’re after a cozy vegetarian dinner—maybe with a leafy salad and a glass of wine.
Kitchen Tools I Use (Nothing Fancy)
I’m not one for complicated gadgets—here’s what I usually use:
- Large pot (for boiling squash and potatoes)
- Potato masher (I like mine a bit old-school, with the zig-zag wires)
- Skillet for the onions
- 9×13″ casserole dish
- Cheese grater (freshly grated cheese melts so much better)
- A good chef’s knife and sturdy cutting board
Storing Leftovers (If You’re Lucky Enough to Have Any)
This gratin stores beautifully. I pop leftovers into an airtight container and refrigerate for up to 3 days. To reheat, just cover with foil and warm it in the oven at 350°F until heated through.
It also freezes pretty well. Let it cool completely, wrap it tight, and freeze for up to a month. Just thaw in the fridge overnight and reheat in the oven.
Acorn and Butternut Squash Gratin Casserole
Creamy, cheesy, and full of cozy flavor—this Acorn and Butternut Squash Gratin Casserole is a real showstopper on the fall table. Made with tender winter squashes, soft roasted garlic, golden potatoes, and melty Gruyère, it’s one of those side dishes that could steal the spotlight at Thanksgiving or any comforting dinner. It’s rustic, French-inspired, and totally worth the oven time.
Ingredients
- 1 large butternut squash, peeled and cubed into 1-inch pieces
- 1 large acorn squash, peeled and cubed into 1-inch pieces
- 4 medium yellow potatoes, sliced about ¼-inch thick
- ½ large sweet onion, chopped
- 1 head of garlic
- 1 tablespoon olive oil (for sautéing)
- ½ teaspoon dried thyme
- ½ teaspoon freshly grated nutmeg
- 1 cup whole or 2% milk
- 3 cups shredded Gruyère cheese (about ½ lb)
- Salt and pepper, to taste
Instructions
- Start by roasting the garlic. Slice the top off a whole head, drizzle it with olive oil, season with a little salt and pepper, then wrap it in foil. Roast it at 400°F for about an hour. Once done, let it cool slightly, then squeeze the cloves out of the skins. Leave the oven on.
- If you’re working with whole squashes, cut them in half and microwave briefly—about 2 minutes—just to soften them up for peeling. Once peeled, cube both the acorn and butternut squash.
- Bring a large pot of salted water to a boil. Add the cubed squash, reduce to a simmer, and cook uncovered until just fork-tender, around 20 minutes. Drain and set aside.
- In a separate pot, add sliced potatoes to salted water. Bring to a boil, then lower the heat and simmer with the lid on until tender, about 10 minutes. Drain and set aside.
- While the vegetables cook, heat olive oil in a skillet over medium heat. Add the chopped onions and dried thyme. Season lightly with salt and pepper, then cook until soft and translucent—about 5 minutes. Add the roasted garlic cloves to the skillet, gently smashing them with a spoon to combine with the onions.
- In a large bowl, mash the drained squash roughly with a potato masher. Fold in the onion-garlic mixture, then stir in the nutmeg and a little more salt and pepper. Taste and adjust the seasoning if needed.
- Gently mix in the cooked potato slices until everything is well combined.
- Spread the vegetable mixture into a 9x13-inch baking dish. Pour the milk evenly over the top. Finish with a generous layer of shredded Gruyère cheese.
- Bake uncovered at 400°F for 30 minutes, or until the top is golden and bubbling. Let it rest for a few minutes before serving.
Nutrition Information
Yield
8Serving Size
1Amount Per Serving Calories 323Total Fat 16gSaturated Fat 9gTrans Fat 0gUnsaturated Fat 7gCholesterol 49mgSodium 367mgCarbohydrates 29gFiber 4gSugar 4gProtein 17g
dinnerbytes.com, occasionally offers nutritional information for recipes contained on this site. This information is provided as a courtesy and is an estimate only. This information comes from online calculators. Although dinnerbytes.com attempts to provide accurate nutritional information, these figures are only estimates.
More Squash Recipes I Rotate Through
When squash season hits, I try to make the most of it. Here are a few others I love:
- Roasted Butternut Squash and Feta Pierogi (comfort food at its best)
- Acorn Squash stuffed with lentils and veggies (great for meatless nights)
- Butternut Squash and Beef Stew (hearty and a little unexpected)
- Creamy Butternut Squash and Mushroom Soup (perfect with crusty bread)
If you’re planning your holiday menu or just craving something rich and cheesy, give this Acorn and Butternut Squash Gratin a spot on the table. It’s cozy, comforting, and full of flavor—everything I want in a fall casserole.
Let me know how it turns out in your kitchen. I’d love to hear what you served it with!
Try Other Butternut Squash Recipes:
