This butternut gratin with walnuts is the kind of cheesy comfort food the French adore. Sweet roasted squash and tender leeks bake together under bubbling Gruyère cheese with a crunchy walnut topping. It's an easy, family-friendly dish that's perfect for cosy dinners or as a festive side for Thanksgiving. It's my idea of playing squash in Autumn and Winter!
Made this tonight with substitutes...mushrooms for chestnuts and beets greens and scallions for leeks. It made a delicious flavor profile. I look forward to trying again with the original ingredients. - Susanne
Ingredients for Butternut Gratin with Walnuts
The base of this simple butternut gratin recipe is roasted butternut squash, softened just enough to slice easily. It's combined with sautéed leeks, chestnuts, and a touch of fresh sage - it goes so well with squash. If you prefer other fresh herbs, then use thyme or rosemary.
Incidentally, in France, we call butternut squash simply 'butternut' with a French accent - there's no translation and it's found easily at the market.
I use Gruyère or Comté cheese, which melt beautifully, but you can mix in Parmesan or sharp cheddar for a stronger flavour. Smoked bacon adds richness and depth, though you can easily leave it out for a vegetarian version. The dish stays just as delicious thanks to the creamy vegetables and toasted walnuts.
The French love chestnuts so much during the festive season, I've created their own chestnut market page. However, if you can't find them, add fried mushrooms or more walnuts.
How to Prepare the Butternut Squash
Cutting raw butternut squash can feel like wrestling with it. My lazy (and safe) trick: prick the skin a few times with a fork and roast it whole for about 20 minutes at 200°C/400°F. The skin will blister slightly, making it much easier to peel and slice afterwards.
If you're short on time, pierce it and pop it in the microwave for about 10-12 minutes instead. Once softened and cooled, scoop out the seeds, cut the flesh into chunks, and it's ready to join the leek and bacon mixture in the dish.
Butternut needs the skin removed but if you want to make this with red kuri squash, then roast it but you can eat the skin, so no need to peel.
Love squash? Get more recipes and facts in the
French market page on Squash and Pumpkins
How to Make It
While the squash roasts, gently sauté the leeks, bacon and sage in olive oil until soft. Combine them with the softened butternut, chestnuts, cream (or crème fraîche), nutmeg, salt and pepper. Top generously with the cheese and walnuts, which toast beautifully in the oven as the gratin bakes.
After about 35 minutes, the kitchen smells incredible; the top turns golden and crisp while the inside stays creamy and full of flavour. As certain members of our family adore bacon, I added a little more to the top to crisp up while it baked.
When to Serve It
This gratin is ideal as a main dish with a simple green salad or as a side with roast chicken or turkey. It's especially popular at Thanksgiving or autumn gatherings - and a wonderful way to use up Hallowe'en pumpkin leftovers by swapping in your favourite squash variety.
If you love gratins, then enjoy French potato classics such as Gratin Dauphinois (with or without cheese) and Gratin Savoyarde, extra cheesy without the cream.
Butternut Gratin with Walnuts
Equipment
- non-stick frying pan with lid
- Dutch oven or gratin dish (23x33cm / 9x13 inch)
Ingredients
- 500 g (18oz / 3½ cups) butternut squash (weight with seeds removed), cut into small cubes
- 2 tablespoon olive oil
- 2 leeks sliced
- 100 g (4 oz) smoked bacon
- 150 g (5½ oz / ¾ cup) pre-cooked chestnuts I use vacuum-packed but in jars or tins are good too *
- 150 g (5½ oz/ ¾ cup) heavy cream or full fat crème fraîche
- 175 g (6oz/ 2 cups ) Gruyère cheese or Comté, grated
- 50 g (2oz/ 3 tbsp) walnuts
- ¼ teaspoon ground nutmeg
- salt & black pepper to taste
- 1 tablespoon fresh sage or parsley finely chopped
Instructions
- Preheat the oven to 200°C/400°F (180°C fan/Gas 6).Prick the butternut squash's skin and roast it whole in the oven for 20 minutes directly in the gratin dish or Dutch oven until the skin starts blistering. Remove and leave to cool slightly. Alternatively, prick the skin and put on high in the microwave for 12 minutes.
- Meanwhile, heat the olive oil in a large non-stick frying pan and gently sauté the sliced leeks, bacon and sage for 2 minutes on medium heat, then reduce to low and cover for about 10 minutes until softened. Set aside.
- When the squash is cooler and easier to handle, cut off the skin and cut in 2 using a good knife. Remove the seeds with a spoon and cut the softened squash into small chunks.
- In the gratin dish, throw in the slightly softened squash chunks, the leeks and bacon mixture and chestnuts. Stir in the cream or crème fraîche, nutmeg, plus salt and pepper to taste. Top with the cheese, walnuts and more sage.
- Bake in the oven for about 35 minutes or until the cheese is bubbling and golden and forms a slight crust. If you prefer yours without the crispiness, then bake for slightly less.
Notes
This recipe post was first published 4 December 2018 but is now completely updated.
Norma Gosling
This is a truly delicious dish which I have cooked every week since reading Jill’s excellent recipe and which has been appreciated by everyone who has tried it.
It is easy to make, even allowing some previous preparation the day before.
I substituted dry fried mushrooms, as Jill suggested, for bacon when feeding vegetarians.
Altogether a welcome addition to my repertoire, thank you!
Jill Colonna
Hi Norma,
I'm so thrilled to hear you love this butternut gratin recipe and it's part of your loved menus at home! Thank you so much for taking the time to review. It means the world. Bon week-end, Jill x
Susanne
Made this tonight with substitutes...mushrooms for chestnuts and beets greens and scallions for leeks. It made a delicious flavor profile. I look forward to trying again with the original ingredients.
I do have a question: the cheese hardened and became like a crust. I assume that it shouldn’t have. Any suggestions?
I really like your website and look forward to visiting Paris in the future,
Jill Colonna
This is the whole point of this French gratin is having the cheese crust - my family fight for the best crispy cheese bits stuck to the sides! Is this why I only got 4 stars for the review? What a giggle. As a result, I shall update the post to explain that it's the whole point.
I'm glad you liked it, though and look forward to hearing you making it with the ingredients in the recipe - it's lovely with them.
June S
A perfect recipe after Halloween to cook the pumpkins. Printed it out to keep in my boook.
Jill Colonna
Goody - thanks for that.
Mimi
The only thing I ever knew about chestnuts were the stories of my French grandmother’s attempts at roasting them and the subsequent sound of gunfire. She had a weekend home in Charmes la Cote that I remember well. An ancient stove but she was the only one with a modern toilet! In any case, I’m grown up now and know that if I ever get my hands on fresh chestnuts that I will carve an X into them before roasting!
Jill Colonna
That sounds idyllic, Mimi. These are such precious memories. I love the smell of the guys selling roasted chestnuts at the top of the metro entrances in winter - but much better if they're roasted over an open fire, sitting by the fireplace. Much more romantic!
Christina | Christina's Cucina
Not a chestnut fan (Mum loves them), but walnuts are more my cup of tea! And of course leeks! YUM! You've got so many fabulous recipes here, Jill! Thank you for sharing them all!
Jill Colonna
Thanks so much, Christina. Glad you like it!
Thomasina
This looks a wonderful winter comforter Jill. Thank you for the inspiration. Thank you also for how to roast pumpkin seeds. Will sus out the cheese for a vegetarian friend coming to stay. And I love chestnuts at Christmas time.
Jill Colonna
Glad you also love the chestnuts! In France, it's not Christmas without them. Not all vegetarians are strict on the cheese, however, as most of them use animal rennet but goats cheese is a good bet for strict vegetarians and many supermarkets have vegetarian cheeses. I know many vegetarians that turn a deaf ear to that, as bubbling cheese on a gratin is too good.
Sarah
I adore chestnuts and my husband too! This looks so delicious Jill - look forward to making this soon. I can see this as a Christmas dish for our 2 vegetarians, although we'll need to check on the cheese.
Jill Colonna
Great idea for a vegetarian Christmas, Sarah. I'm not sure of the cheeses since I'm not a full vegetarian myself (although don't eat red meat or lamb anymore). So glad you'll make it. Enjoy!