Winter Vegetable Gratin Gruyere

I threw this together on a gray January afternoon when the farmers market had rows of root vegetables but nothing green in sight. The house smelled like butter and cheese for hours. My neighbor knocked to ask what I was cooking, and I ended up slicing her a corner while it was still too hot to handle properly.

The first time I made this for a dinner party, I panicked because the top wasn't browning. I cranked the broiler for two minutes and it went from pale to perfect. Now I do that every time, standing there with the oven light on like I'm watching a campfire.

Ingredients

• Butternut squash: Adds natural sweetness and soaks up the cream beautifully. Slice it thin so it cooks evenly with the potatoes.
• Parsnips: They taste like carrots grew up and got interesting. Don't skip them or you'll lose that earthy backbone.
• Yukon Gold potatoes: Waxy enough to hold their shape but still creamy. Russets turn to mush here, trust me.
• Leeks: Mild onion flavor that doesn't overpower. Rinse them well because dirt hides between every layer.
• Unsalted butter: The base of the sauce. I always use unsalted so I can control the salt level myself.
• All-purpose flour: Thickens the sauce into something that clings to every vegetable slice. For gluten-free, use a 1:1 substitute.
• Whole milk and heavy cream: This is not the time for skim milk. The richness is the point.
• Ground nutmeg: A little goes a long way. It makes the whole dish smell like a secret.
• Gruyere cheese: Nutty, melty, slightly sweet. The star of the show.
• Parmesan cheese: Adds sharpness to the breadcrumb topping and helps it turn golden.
• Fresh breadcrumbs: I make mine from day-old bread. They crisp up better than store-bought.
• Olive oil: Tossed with the breadcrumbs so they don't just sit there pale and sad.
• Fresh thyme: Optional but worth it. The leaves release their oil in the oven and perfume everything.

Instructions

Preheat and prep your dish:

Set the oven to 375°F and butter your baking dish generously. Don't skip the butter or the edges will stick and you'll lose the best crispy bits.

Slice the vegetables:

Aim for about 1/8-inch thickness so everything cooks at the same rate. A mandoline makes this fast, but a sharp knife and patience work just as well.

Make the roux:

Melt the butter in a saucepan over medium heat, then stir in the flour and cook for a minute until it smells toasty. This step cooks out the raw flour taste.

Build the sauce:

Slowly whisk in the milk and cream, stirring constantly so no lumps form. Keep whisking until it thickens enough to coat the back of a spoon, about 3 to 5 minutes.

Season the sauce:

Stir in nutmeg, salt, and pepper, then pull it off the heat. Taste it now because once it's baked, it's too late to fix.

Layer the vegetables:

Arrange half the vegetables in overlapping rows or casual piles, whatever feels right. Sprinkle with half the Gruyere, then repeat with the remaining vegetables and cheese.

Pour the sauce:

Drizzle the warm sauce evenly over the top, letting it seep into the layers. Tilt the dish gently to help it spread.

Prepare the topping:

Toss breadcrumbs with Parmesan, olive oil, and thyme in a small bowl. Scatter it over the gratin like you're tucking it in.

Bake covered:

Cover loosely with foil and bake for 30 minutes. The foil traps steam so the vegetables cook through without drying out.

Finish uncovered:

Remove the foil and bake another 20 minutes until the top is golden and the edges bubble. If it's not browned enough, hit it with the broiler for 2 minutes.

Rest before serving:

Let it sit for 10 minutes so the sauce thickens and you don't burn your mouth. This is the hardest part.

Pin It

My dad, who claims he doesn't like vegetables, ate two servings of this and asked if there was more in the fridge. I didn't tell him it was mostly root vegetables until he was halfway through round two.

Swaps and Variations

You can swap in sweet potatoes, carrots, or even thinly sliced fennel if that's what you have. I've made this with celery root once and it was deeply savory. If you want a little heat, whisk a pinch of cayenne into the sauce. For a vegan version, use plant-based butter, milk, cream, and cheese, just know the sauce won't thicken quite as much so you might need an extra teaspoon of flour.

Storage and Reheating

Leftovers keep covered in the fridge for up to four days. Reheat in a 350°F oven until warmed through, about 20 minutes. The microwave works in a pinch but the topping won't crisp back up. I've frozen this before baking with decent results, just thaw it overnight in the fridge first.

Serving Suggestions

This is rich enough to be a main dish with a simple green salad and crusty bread. It also works beautifully as a side for roast chicken or beef. I like it with a crisp white wine, something with acidity to cut through the cream.

• Serve it straight from the baking dish for a casual family dinner.
• Pair it with roasted Brussels sprouts or a bitter green salad to balance the richness.
• Make it the day before a holiday and bake it while the main dish rests.

Pin It

This is the kind of dish that makes January feel a little less gray. I hope your kitchen smells as good as mine did.

Recipe FAQs

→ What vegetables are used in this gratin?

Butternut squash, parsnips, Yukon Gold potatoes, and leeks are thinly sliced and layered for the gratin.

→ Which cheeses provide flavor and texture?

Gruyere offers a nutty creaminess while Parmesan adds a savory, crunchy topping when combined with breadcrumbs.

→ How is the sauce prepared for the gratin?

A velvety sauce is made by cooking butter and flour, then whisking in milk, cream, nutmeg, salt, and pepper until smooth and thickened.

→ Can this dish be adapted for dietary restrictions?

Yes, gluten-free flour and breadcrumbs can be used, and plant-based milk, cream, and cheeses make it suitable for vegan diets.

→ What is the recommended baking method?

Bake covered with foil for 30 minutes to allow even cooking, then uncovered for 20 minutes to achieve a golden, bubbly top.

→ Are there suggested variations for vegetables?

Sweet potatoes or carrots can replace some root vegetables to modify the flavor and texture profile.