This Butternut Squash and Sage Gratin is a delicious, cheesy side dish similar to scalloped potatoes. Sweet, thinly sliced butternut squash bakes in a creamy Fontina and Parmesan sauce, then gets topped with crunchy panko breadcrumbs and baked until golden. It’s an ideal addition to your Christmas or Thanksgiving dinner table.

A cast iron skillet of butternut squash and sage gratin with serving spoons

Table of contents

Ingredients

  • Butternut squash
  • Butter
  • Flour
  • Milk
  • Fontina cheese
  • Parmesan cheese
  • Fresh sage leaves
  • Nutmeg
  • Salt
  • Black pepper
  • Panko breadcrumbs

What is gratin?


Any dish prepared the French way, au gratin, means you bake it in cream or milk with cheese. This recipe adds a little twist with panko breadcrumbs for a lovely, crunchy topping.

Gratin serving dish


I recently purchased some small cast iron skillets because they’re just so cute. You can cook in them and serve the food right in the pan. I had a couple of leftover butternut squash from making Thai Butternut Squash Soup, so I came up with this gratin.


If you don’t have cast iron skillets, you can also make the recipe in an 8 x 8-inch (23 x 23 cm) square or oval baking dish.

Tried and true gratin recipe


If you’ve ever made a gratin or scalloped potatoes, you know the milk or cream can curdle and the cheese can separate, creating an oily layer. This is my foolproof recipe that avoids both issues. This gratin recipe has stood the test of time — it’s been a favorite since I first shared it in 2014 and remains just as popular today.

The inside of butternut squash gratin showing the bright orange squash and creamy cheese sauce


Tips for Making Butternut Squash Gratin

1. Choose the right squash.
Look for a firm butternut squash with a smooth, blemish-free skin. Smaller squash tend to be sweeter and less watery.

2. Slice evenly.
Cut the butternut slices into uniform rounds or cubes so they cook evenly. A sharp knife or mandoline works best.

3. Pre-cook if needed.
If you want to speed up baking, lightly steam or sauté the squash slices before layering—they’ll finish tender in the gratin faster.

4. Preheat oven.
A hot oven ensures the cheese sauce bubbles evenly and the top gets golden and crispy while the squash cooks through

5. Layer thoughtfully.
Alternate squash with cheese sauce in even layers, and don’t overload – too thick a layer may take longer to cook through.

6. Cheese choice matters.
Use a combination of creamy Fontina with Parmesan for richness and a golden crust. A sprinkle of extra Parmesan with the breadcrumbs adds more flavor.

7. Bake uncovered.
This ensures a golden, bubbly top while the interior cooks perfectly. Tent with foil if the top browns too quickly.

8. Let it rest.
Allow the gratin to sit 5–10 minutes after baking; it will firm up slightly and make serving easier.


Instructions for cutting up a whole butternut squash


Cut off the top end of the squash.

Cutting the top off a butternut squas

Peeling butternut squash


Peel the entire squash.


Cut the long neck as close to the bulbous end as possible. This is especially helpful for this recipe, as it lets you cut as many rounds as possible.

3 pieces of a butternut squash
Removing seeds from a squash


Cut the bulbous part in half and use a spoon to scrape out the seeds.


Chop the squash flesh to the size needed for your recipe. In this case, slice thinly.

A cutting board with sliced butternut squash, fresh sage, parmesan cheese and grated fontina viewed from overhead

Slicing butternut squash


When it comes to slicing the butternut squash, I recommend using a mandolin. The thinner the slices, the faster it bakes.


The best butternut squash for gratin


Choose a long-neck butternut squash so you can cut plenty of circles for the gratin. Use a mandolin to get thin, even slices, unless you can slice very thinly with a sharp knife.

Gratin cheese sauce


For the sauce, I took inspiration from the Baked Gnocchi with Sage and Cheese I made last year. The cheese sauce was so good, it had to be repeated.

Best cheeses for gratin


I always recommend using any good melting cheese you enjoy when making a cheese sauce. I can’t always find Fontina at my store, so Gruyère is a delicious alternative. Sharp white cheddar or Havarti also melt beautifully. A reader recently suggested trying a mild Gorgonzola for a unique twist. For the panko topping, Parmesan is the best choice to add a nutty, golden crust.

2 butternut squash and sage gratins in mini cast iron skillets

Panko topping


I choose panko breadcrumbs over regular to add more of a light, crunchy texture on the top of the gratin. To make also use gluten-free breadcrumbs.

2 mini cast iron skillets with butternut squash and sage gratin on a baking sheet ready for the oven

The perfect holiday side dish


This creamy Butternut Squash Gratin is the ultimate holiday side dish. Perfect for Thanksgiving, Christmas, or any festive meal, it’s rich, cheesy, and irresistible. Feeding a crowd? Simply double the recipe and bake it in a 9 x 13-inch (23 x 33 cm) dish. It was such a hit at Thanksgiving that it quickly became a Christmas repeat request!

Butternut squash gratin leftovers


Allow the gratin to cool completely before storing. Transfer leftovers to an airtight container in the refrigerator for up to 3–4 days. For longer storage, you can freeze portions in a freezer-safe container for up to 2 months. When ready to eat, reheat in the oven until warmed through to keep the top crispy, or microwave individual servings for a quick meal.


They taste just as delicious when reheated. Warm it in the oven until bubbly, or microwave a single serving for a quick snack. 


Leftovers also make a perfect side for another meal, pairing beautifully with Roast Chicken, Pork, or a vegetarian main.

If you’ve tried my Butternut Squash and Sage Gratin, please leave a star rating in the recipe. You can also leave a comment or ask a question below.

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An overhead view of butternut squash gratin
5 from 27 reviews

Butternut Squash and Sage Gratin

Janette
Sweet and creamy butternut squash, fontina & parmesan cheese sauce with fresh sage. 
Prep Time: 15 minutes
Cook Time: 40 minutes
Total Time: 55 minutes
Servings: 4
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Ingredients
 

  • 1 pound (226 grams) butternut squash , peeled and sliced (see note)
  • 4 tablespoons unsalted butter
  • 4 tablespoons all-purpose flour
  • 2 cups (272 ml) whole milk
  • 1 cup (50 grams) fontina cheese, grated
  • 2 cups (100 grams) Parmesan cheese, freshly grated
  • 1 tablespoon fresh sage, chopped
  • ¼ teaspoon freshly grated nutmeg
  • ¼ teaspoon ground black pepper
  • Salt to taste
  • ½ cup (40 grams) panko breadcrumbs

Instructions
 

  • Preheat oven to 375°F/190°C.
  • Butter an 8 x 8-inch (20 x 20-cm) baking dish or mini cast iron skillets.
  • Melt the 4 tablespoons butter in a pan over medium heat. Whisk in the flour until it absorbs the butter. Cook while stirring for 2 minutes to cook out the flour taste, it will start to turn darker when ready. Slowly whisk in the milk until thickened. Stir in the fontina and half of the Parmesan cheese until completely melted and sauce is smooth. Stir in the sage, nutmeg and pepper. Taste the sauce and taste for salt. This will depend on how salty your cheese is.
  • Arrange ⅓ of the butternut squash slices in a single layer, slightly overlapping on the bottom of the dish.
  • Pour ⅓ of the sauce over the first layer of butternut squash. Arrange another single layer of butternut squash and top with ⅓ of the sauce. Arrange the last layer of butternut squash and top with the remaining sauce.
  • Mix the rest of the Parmesan cheese with the panko and mix well. Top the gratin with an even layer of the panko and a little more sage if desired.
  • Place the dishes onto a baking sheet, cover with foil and bake for 30 minutes. Time will depend on how thickly you sliced the squash. Remove the foil and continue to bake until the top is golden and the butternut squash is tender when a fork is inserted. 
  • Remove from the oven and allow to sit for 5 minutes before serving.

Notes

Choose a butternut squash with a long neck so you can cut in circles.
 
Serving: 1, Calories: 631kcal, Carbohydrates: 41g, Protein: 30g, Fat: 40g, Saturated Fat: 23g, Polyunsaturated Fat: 13g, Cholesterol: 121mg, Sodium: 1300mg, Fiber: 5g, Sugar: 10g
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