If you’re looking for a comforting fall side that feels both cozy and a little fancy, I’ve got you covered with my Butternut Squash Gratin with Leeks, Sage, and Walnuts Recipe. This dish is packed with layers of tender butternut squash, savory leeks, fragrant sage, and crunchy walnuts—all baked together with creamy goodness and melted cheese. Trust me, once you try this, it’ll become a staple on your holiday table or anytime you want something warm, silky, and satisfying.

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Why You’ll Love This Recipe

Bursting with Layers of Flavor: The combination of buttery squash, caramelized leeks, and earthy sage creates a rich, harmonious taste experience.
Simple Ingredients, Big Impact: You only need a handful of ingredients and some basic kitchen skills to whip this up beautifully.
Versatile and Adaptable: Whether you’re vegan, gluten-free, or just love variations, this dish can be tweaked to suit your preferences.
Perfect for Entertaining or Everyday: It looks and tastes like a showstopper but is easy enough for weeknight dinners.

The image shows a round white dish filled with a layered casserole. The top layer is made of thin orange slices that look soft and slightly cooked, scattered with a few green leaves for garnish. Underneath, there is a creamy layer mixed with small brown bits. A wooden spoon is lifting a portion from the dish, showing the layers clearly: the bright orange slices on top, the creamy light-colored middle, and the little brown pieces mixed in between. The dish is placed on a white marbled surface with a blurred cloth and some green leaves in the background. The photo was taken with an iphone --ar 4:5 --v 7

Ingredients You’ll Need

Each ingredient plays a special role here—juicy butternut squash adds sweetness, leeks bring a gentle onion flavor, and sage adds that rustic, woodsy note. Plus, walnuts give an unexpected crunch that’s just wonderful. When shopping, look for fresh sage and firm squash for best results.

Butternut Squash: Choose a firm, heavy squash with smooth skin for easy peeling and the best texture when sliced thin.
Olive Oil or Butter: I usually go butter for richness but olive oil keeps it lighter and works great if you want a dairy-free option.
Leeks: Make sure to clean well; they can trap grit between their layers. The thin slices soften and add subtle sweetness.
Garlic: Use fresh cloves for that mellow, aromatic boost.
Sage Leaves: Fresh sage tastes far superior to dried here—chop some into the cream sauce and keep a few whole for optional crispy garnish.
Heavy Cream or Coconut Milk: Heavy cream adds luxury and depth, but coconut milk is an excellent vegan-friendly substitute that keeps it creamy.
Salt and Pepper: Season carefully to make all the flavors pop without overpowering the squash.
Nutmeg: Just a pinch gives the gratin that classic warmth and depth that’s so comforting.
Onion Powder: This is optional but adds a nice little seasoning boost if you want it.
Water: Helps steam the squash slices gently as the gratin bakes, so everything cooks through beautifully.
Gruyere Cheese: I love the nutty meltiness of gruyere, but parmesan or a vegan parmesan alternative works just fine.
Walnuts: Chopped for texture and a toasty surprise in every bite.

Note: You’ll find the complete list of ingredients, along with their exact measurements, in the printable recipe card at the bottom of this post.

Variations

One of the things I love about this Butternut Squash Gratin with Leeks, Sage, and Walnuts Recipe is how easily it adapts to your tastes or dietary needs. Don’t be afraid to make it your own!

Vegan Version: Swap heavy cream for full-fat coconut milk and use vegan parmesan or nutritional yeast instead of regular cheese. It’s surprisingly delicious and creamy!
Nut-Free Option: Leave out the walnuts or substitute with pumpkin seeds for crunch while keeping it allergy-friendly.
Cheese Variations: Gruyere is my top pick, but cheddar, fontina, or mozzarella will work nicely too if you want a different vibe.
Herb Swaps: If you don’t have fresh sage, try thyme or rosemary for a new flavor twist.

How to Make Butternut Squash Gratin with Leeks, Sage, and Walnuts Recipe

Step 1: Prepare Your Squash and Leeks

Start by peeling your butternut squash and slicing it into thin 1/8-inch disks—I find a sharp mandoline is a godsend here to keep the slices consistent, which helps everything cook evenly. Next, thinly slice your leeks and give them a good rinse to remove dirt. This is key! Roughly chop the garlic and finely chop the fresh sage leaves you’ll be folding into the creamy sauce. Trust me, fresh herbs make a massive difference.

Step 2: Cook the Leeks and Garlic

Heat your olive oil or butter in a pan over medium heat. Toss in the leeks and garlic, cooking gently until soft and fragrant—about 6-8 minutes. You want them meltingly tender but not browned. Then stir in the chopped sage and cook for another minute to release its flavor.

Step 3: Make the Creamy Sage Sauce

Pour in the heavy cream (or coconut milk) to the leek mixture. Add salt, pepper, nutmeg, and onion powder if using. Stir everything together and let it simmer gently for 3-4 minutes to marry the flavors. This sauce will be your gratin’s soul, so taste and adjust seasoning now.

Step 4: Layer and Bake

In a buttered or oiled baking dish, layer the butternut squash disks overlapping slightly. Pour over the creamy leek and sage sauce, sprinkle chopped walnuts and grated gruyere cheese on top, then add a splash of water to the bottom to help with steam. Cover it loosely with foil and bake at 350°F (175°C) for about 50 minutes. Remove foil and bake another 10-15 minutes until the top is bubbling and golden brown.

Step 5: Optional Crispy Sage Garnish

For an extra special touch, I like to fry a few whole sage leaves in a bit of olive oil until crisp and use them to garnish the gratin just before serving. It adds so much aroma and a beautiful pop of color.

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Pro Tips for Making Butternut Squash Gratin with Leeks, Sage, and Walnuts Recipe

Perfect Slice Thickness: I’ve found slicing the squash to 1/8 inch ensures it cooks through perfectly without turning mushy.
Leek Cleaning Is Key: Leeks can trap grit, so slice and soak them in cold water before using to avoid surprises in your gratin.
Don’t Skip the Nutmeg: This little spice really uplifts the whole dish in a subtle but essential way.
Watch Your Bake Time: If you skip covering the dish early, the top might burn before the squash softens—cover with foil for most of the bake!

How to Serve Butternut Squash Gratin with Leeks, Sage, and Walnuts Recipe

The dish is a baked layered casserole in a white bowl, featuring visible round, thin orange slices of cooked vegetables arranged neatly on top, likely sweet potatoes or squash. The top layer shows a golden-brown crumbly texture with small bits of chopped nuts and some fresh green herb leaves scattered inside and on top. A wooden spoon is lifting a portion from the bowl, revealing creamy, soft layers beneath the top orange slices, mixed with melted cheese and herbs. The background is a white marbled surface with a few green herb leaves placed near the bowl. The photo taken with an iphone --ar 4:5 --v 7

Garnishes

I usually top mine with those crispy fried sage leaves I mentioned earlier and a sprinkle of extra chopped walnuts for texture contrast. Sometimes, a little fresh thyme brightens it up beautifully as well.

Side Dishes

This gratin shines alongside roast chicken, pork tenderloin, or even a hearty lentil stew. I also love serving it with a simple green salad dressed with lemon vinaigrette to cut through the creaminess.

Creative Ways to Present

For holiday dinners, I like to serve this gratin in individual ramekins—everyone gets their personal golden, bubbling portion. It makes the meal feel extra special and festive with minimal fuss.

Make Ahead and Storage

Storing Leftovers

I store leftovers covered tightly in the fridge for up to 3 days. It reheats well and actually tastes better the next day once the flavors meld a bit more.

Freezing

Because of the cream and cheese, freezing isn’t my first choice, but if you need to, freeze in airtight containers and thaw overnight in the fridge before reheating. The texture may be a touch softer but still delicious.

Reheating

I reheat leftovers covered with foil in a 325°F oven until warm, which keeps it from drying out. Alternatively, microwaving works if you’re short on time, but watch so it doesn’t overcook.

FAQs

Can I use frozen butternut squash for this gratin?

While fresh butternut squash gives the best texture and flavor, you can use frozen squash in a pinch. Just be sure to thaw and pat it dry thoroughly to avoid excess water making the gratin soggy.
Is this gratin suitable for vegans?

Absolutely! Swap the heavy cream for coconut milk and use vegan cheese alternatives, like nutritional yeast or vegan parmesan, to keep it creamy and flavorful while staying plant-based.
Can I prepare this gratin ahead of time?

Yes! You can assemble the dish and cover it, then refrigerate for up to 24 hours before baking. This makes it easy to prep for holiday meals or busy weeknights.
What can I substitute for gruyere cheese?

Gruyere adds a nutty, melty quality, but you can substitute with parmesan, fontina, cheddar, or mozzarella depending on your preference and what you have on hand.

Final Thoughts

I absolutely love how this Butternut Squash Gratin with Leeks, Sage, and Walnuts Recipe balances subtle sweetness with savory depth and a pleasing crunch. It’s one of those dishes that feels like a warm hug on a plate and impresses guests without any stressful fuss. If you’re ready for a fall favorite that’s both comforting and elegant, this recipe is definitely the one to try. I can’t wait for you to make it and share it with your loved ones!