Celery Root and Squash Gratin with Walnut-Thyme Streusel Recipe
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Make the most of fall ingredients with this seasonal gratin, in which layers of celery root and squash are bathed in cream and topped with crunchy walnut- and thyme-studded breadcrumbs.
What to buy: Panko is coarse Japanese-style breadcrumbs. It’s available in the international section of most supermarkets.
Game plan: You can make the gratin up to 1 day ahead and rewarm it, covered, at 350°F for about 20 to 30 minutes before serving.
This recipe was featured as part of our Neoslacker Interactive Thanksgiving menu.
INGREDIENTS
For the streusel:
- 1 cup panko
- 4 tablespoons unsalted butter (1/2 stick), melted
- 1/2 cup finely chopped walnuts
- 1 tablespoon finely chopped fresh Italian parsley
- 1 1/2 teaspoons fresh thyme leaves
- 1 teaspoon kosher salt
For the gratin:
- 1 (3-pound) butternut squash
- 1 1/4 cups heavy cream
- 1 medium celery root, also known as celeriac (about 1 pound), peeled and cut in half
- 2 tablespoons unsalted butter (1/4 stick), plus more for coating the baking dish
- 1/2 medium white onion, thinly sliced
- Kosher salt
- Freshly ground black pepper
INSTRUCTIONS
For the streusel:
- Combine all ingredients in a medium bowl and mix until the butter is incorporated. Cover and place in the refrigerator until ready to use.
For the gratin:
- Heat the oven to 400°F and arrange a rack in the middle. Coat a 13-by-9-inch baking dish with butter and set aside.
- Prepare the squash: Peel off the skin with a vegetable peeler.
Trim the top and bottom. 
Cut the neck from the bulb of the squash. 
Halve each piece lengthwise and scrape out the seeds. 
- Pour the cream into a large bowl and set aside. Slice the squash and celery root into 1/4-inch-thick pieces with a mandoline or sharp knife, placing the pieces in the cream as they are cut. Toss until well coated.
- Melt the butter in a medium frying pan over medium heat. When it foams, add the onion and season well with salt and pepper. Sauté until soft and translucent, about 5 minutes; set aside.
- Construct the gratin by ladling a third of the squash–celery root mixture into the prepared baking dish, then seasoning well with salt and pepper. Top with half of the onions, then another layer of squash and celery root. Season the second layer with salt and pepper and cover with the remaining onions. Place the last of the squash and celery root on top and press down to create an even surface. Season with salt and pepper, then pour the remaining cream over top.
- Sprinkle the streusel evenly over the gratin. Bake until the vegetables are soft and the streusel is golden brown, about 40 to 50 minutes. Let sit at room temperature for about 20 minutes before serving.
Has anyone frozen this dish as a make-ahead item? I'm wondering how it would hold up.
Wow, this was amazing, and didn't taste at all heavy like I expected. While it was great with no additions, I think I'll add more herbs or some cheese and nutmeg, like suggested above, to add more flavor next time. Perhaps some walnut oil too, I didn't get much walnut flavor from the streusel unfortunately.
I just have to say, I made this dish during this past Christmas and everyone went just nuts--it was fabulous. Fast forward to last weekend. My son came for a weekend visit and requested I make this dish again--he said it was so awesome! Well, I made it and it tasted even better the second time around. This is now becoming a new family classic!
Thank you so much for a great recipe!
The first time I made this it was amazing - got rave reviews at Thanksgiving. Yes, almonds are a suitable substitute in the topping. However the second time I made the dish it came out bland and the texture wasn't right. I think the problem was using a large squash with less flavor and baking too long so avoid my mistakes and it'll be wonderful!
Second time I made this, each time a show stopper!! Its way too easy..
this was SOOOOOO awesome... a huge hit at the thanksgiving potluck i attended. celeriac is definitely a conversation starter.
this dish looks amazing and i am inspired by the comments... but i am allergic to cow dairy and unfortunately i cannot find goat cream in the U.S. do you think goat milk would work instead of the heavy cream? thanks!
This sounds amazing, I'll definitely try it. Does anyone have a suggestion for a walnut substitute? I'm allergic but the rest of the dish sounds like a winner. Was thinking almonds in this case, but please let me know if you have other ideas. (FYI: allergy is only to walnut, hazelnut and pecan, the rest are fine).
Re: cut celery root, at this point I'm just happy to find it in stores - a year ago I had to go to 3 grocery stores just to find it.
I almost cut off my finger slicing the cerely root, but this is damn good. It took 20 min longer and I covered it with foil after browning the streusel. It will be on my thanksgiving table! Any clue where you can buy pre-cut celery root?
Chefartist -- I wondered the same thing.. I love the idea of a nice, nutty cheese in there, even just mixed in with the streusel top.. Has anyone given this a try?
I made this last week; it was delicious and well received.
Chef, I would forgo the Gruyere and nutmeg. I had the same thought, because it's the classic gratin way, but I don't think this dish needs it.
So delicious. The celeriac adds the little surprise flavor that lifts this gratin way above average. I served it with veal schnitzel and red cabbage. Warning: in my oven the cooking time was closer to 70 minutes than 40, and I think of my oven as fast.
Great idea. Thanks Amy.
Would a lil' Gruyere and nutmeg hurt in this recipe? Just wondering?
Sorry, I am a recvovering "cave-aged Gruyere addict!"
:)
This is a really tasty recipe. It's definitely a staple in my recipe repertoire.
This recipe was really great! I think I'll make it again for Christmas dinner. I've never used celery root before, and this recipe has inspired me to find other ways to use it.