Winter can mean a lot of different things – growing up it meant hot chocolate, sledding, and praying for snow days. Now that I live in Northern California it means intermittent rain, citrus, and running around on the beach (I know, it’s weird here). But despite the differences, winter still means root vegetables – roasted, baked, or made into soups. And for me, root vegetables means celeriac.
Chances are you have seen celeriac, or celery root, at the grocery store, and then walked right by hoping not to catch its eye. I mean, it’s a big knobby thing with weird root protrusions sticking out all over it and probably large clumps of dirt and perhaps some awkward green shoots coming off the top. It is the awkward teenager of the vegetable world and as a result, is not always well loved. But I love it –and no I’m not just trying to be a hipster here; I want everyone to love it. That ugly exterior is easy to cut away and the flavor is surprisingly crisp, juicy, and fresh. Sort of like celery but without the overwhelming greenness and no threads to pick out of your teeth afterwards. Unlike most root vegetables, celeriac is just as good raw as it is cooked and it’s great in winter salads. And that’s great for those times when you just cannot look at another stick of butter – but I haven’t reached that point just yet.
When I think of winter food, I think of hot and filling, stick-to-your-ribs kind of food. And in the vegetable world, that food is gratin. Potatoes are the king of comfort food (or at least in the running) so it seems unfair that they get all the love when it comes to gratin as well. Yes, this gratin has some potatoes too, but the star is really the celeriac. And unlike most gratins it has no cheese. No cheese, you say? Yes, well, it gets along just fine without it thanks. Seriously, I may even prefer this to the traditional cheesy gratin. It’s rich but not dense in the way that a lot of gratins are and as a result it feels just fine to eat two pieces for dinner.
Gratin, like all dishes made of baked vegetables, will turn out best if you make sure to cut all your vegetable pieces to approximately equal widths so they cook evenly. There are two ways to accomplish this: have amazing knife skills or use a mandoline. I took the second route. A year or so ago I bought myself a Benriner mandoline (and some Kevlar gloves to protect my fingers, since I hate that hand guard that comes with it) and I haven’t looked back – it makes meals that much easier to prepare and it takes up very little space in my kitchen.
This gratin is excellent baked in a cast iron pan for extra browning but it would be just as good in a 9 by 13 Pyrex dish. Because it doesn’t have cheese to keep it stuck together, it’s best to cook it ahead of time and reheat it before serving so that it has some time to bind itself together. Or if, like me, you just can’t wait for that first slice, serve it warm from the oven and just a little bit messy.
Inspired by Fennel Gratin in Sunday Suppers at Lucques by Suzanne Goin
1 tbs fennel seeds
1 pound potatoes – preferably Yukon gold or red bliss – I prefer to not peel them and just wash them thoroughly
2/3 cup heavy cream
1 ½ pound celeriac root
1 thinly sliced red onion
1 tbs thyme leaves
1/2 tbs tarragon
1/3 cup olive oil
1 tsp plus 2 tsp kosher salt
Preheat oven to 425F.
Add fennel seeds to a dry pan and place over medium heat. Toast for 2-3 minutes or until seeds are fragrant and barely browned.
Slice the potatoes into 1/16 inch slices – 1/8 if using a knife instead of a mandoline. You may need to halve the potatoes if they’re too big but the resulting slices should be about the same size as the celeriac. Toss the potatoes with cream and 2 tsp salt.*
Cut the ends off the celeriac so it will stand on a cutting board and cut the rest of the outer layer off in strips, working your knife from top to bottom. Quarter the remaining root and slice into approximately 1/16 inch slices (1/8 if using a knife). Add the celeriac slices, fennel seed, thyme, red onion, and olive oil to the potato and cream mixture. Season with 1 tsp salt and mix until well combined.
Grease a 10 inch cast iron skillet or a 9 by 13 Pyrex dish and lined the bottom of the pan with overlapping slices of potato. Arrange the remaining potato and celeriac mixture in the dish.**
Bake the gratin for about 45 minutes, until golden brown in spots and the onions on the top are slightly crispy. Let cool at least 30 minutes before slicing.
*Tossing the potatoes with cream right after they’re cut coats them and prevents them from browning.
** You can choose to artfully arrange all the slices one at a time but I find this tedious. Just lining the bottom will help make it easier to lift out slices and creates some of that tidy pattern without taking as much time.