Fennel and sweet potato gratin is lush and savory inside with a golden, cheesy top. Loaded with fennel and thinly sliced root vegetables, it’s subtle flavors and cozy layers practically melt in your mouth. This is the kind of cool-weather dish I love to serve alongside crispy-skinned roast chicken. And it’s equally soul-satisfying paired with a simple green salad for a delicious vegetarian meal.
Vegetable gratins are one of those dishes you’ll find yourself repeatedly spooning “just a little more of” onto your plate… until you realize you’ve devoured half of the casserole yourself.
Or maybe that’s just me?
What’s a Gratin?
Gratin is actually a technique, not a specific recipe. Ingredients are baked in a shallow dish until they’re tender. Then they’re sprinkled with something that will create a crust. Cheese, breadcrumbs, butter maybe. Finally the whole thing is finished under the broiler so that the top gets nice and golden.
SO many things can be turned into a gratin. But the ingredients under the crisped, golden crusts of my very favorite gratins? That would be thinly sliced vegetables lightly bathed in flavorful cream and topped with a crust of parmesan cheese. It’s that magical contrast of textures that does it for me..creamy and savory inside, crisp and golden outside.
Mmmmmmmm… Divine Vegetable Decadence 🙂
Here’s What You’ll Need
- Olive oil and butter
- Sweet potatoes
- Fresh fennel
- Garlic
- Heavy cream
- Parmesan and gruyere
- Fresh thyme, salt, pepper and nutmeg
Getting Inspired By Produce!
Vegetable gratins are super flexible. Once you get your method down, you might just find yourself doing your own gratin-improv, inspired by what’s in season. Or by what you have hanging out in your pantry, in the crisper of your fridge or tucked away in your cheese drawer.
You can absolutely make this with all orange sweet potatoes and it will be delicious! But look around and see if there’s something else you could add for color or an interesting new flavor. Last spring I’d just discovered delicate, creamy-fleshed creme brûlée sweet potatoes (pictured above). I fell in love with them and they became the inspiration for this recipe. I think slices of butternut squash would be great, too. Or what about sliding in some thinly sliced celery root- it’s wonderful, mildly nutty flavor would be really nice here. Maybe include some sliced shallots and beautiful rainbow carrots cut thinly on an angle?
a rainbow of carrots from The Chef’s Garden 
celery root- funny looking but delicious!
A Few Guidelines To Keep In Mind
If you’re doing your own thing there are a few guidelines to keep in mind when selecting and preparing your produce:
- Choose vegetables that will cook in about the same amount of time.
- Slice them to the same thickness (about 1/8 inch)
- Stick with root vegetables. This gratin doesn’t rely on any thickeners, like flour, so avoid vegetables that release a lot of water when they’re cooked (you don’t want a runny gratin!)
My Favorite Discovery Of 2021
Earlier this year, Hannah and I took our first trip to a farm stand that we’d been hearing wonderful things about. Farmer Jones Farm stand is a roadside produce haven located in Huron, Ohio and I cannot say enough good things about them. The produce they grow is some of the best tasting, most nutritionally dense and beautiful produce you can find anywhere! I’ve been back every other week since and always come home with something unique and new to me that I can’t wait to try.
spring vegetables from Chef’s Garden 
fall vegetables (and a carrot fritter) from chef’s Garden 
with Farmer Lee Jones and my daughters
Chef’s all over the world have been ordering produce from them for years. And until recently it wasn’t available to home cooks like you and me. I’m lucky to live close enough that I can go in person but you don’t have to drive to Huron to enjoy their incredible vegetables! As of this year YOU can order boxes of Chef’s Garden produce delivered TO YOUR DOOR within days of harvest!! How exciting is that?? I’ll be choosing that option through the winter months myself. Because now I’m hooked and nothing I can buy in a grocery store tastes as good.
There’s so much more to what they do at The Chef’s Garden that I could never do them justice here. You can read all about their mission to farm in harmony with nature and their passion for quality and innovation here. You’ll also find incredible recipes that will make you fall in love with vegetables.
But I Digress…
Last week, when I was at the stand, I was giddy when I found my beloved creme brûlée sweet potatoes again! And right next to them were these stunning purple sweet potatoes. I’d already tucked a bunch of baby fennel into my bag because I was craving this gratin, so I picked up a quart of each and knew exactly what I’d be making when I got them home. I couldn’t wait to see those beautiful colors and flavors layered in my gratin dish.
Mis En Place (everything in it’s place)
When making a gratin (or anything else, really) getting all of your ingredients prepped before you start will make your life so much easier!
So after you preheat your oven- also really important- start prepping. Slice your veggies (knife, food processor, mandoline- choose your tool), shred your cheese, chop your garlic and herbs, measure your cream. I also like to combine salt and pepper in a little dish because when assembling the layers your fingers will be wet and you don’t want to be dipping into your salt box or grabbing your pepper mill with sticky hands.
Need Some Help Prepping fennel?
You’ll most likely be using larger, mature fennel bulbs when you make this gratin. It’s not a vegetable most of us cook with everyday and if it’s your first time you might not know exactly how to prep fennel. Here’s what I do:
- Cut off the stems and fronds close to the top of the bulb. Make sure to save the fronds. You’ll be using some of them in the recipe and any extra would be great in salads later in the week!
- Quarter the bulb and remove the hard, wedge-shaped core and any tough outer layers.
- Slice very thinly, crosswise.
Most recently when I made this I used baby fennel. Baby fennel was new to me and I probably should have googled before prepping. I thought, because it was young, that the stems would be more tender than mature fennel. And I had already envisioned them sliced lengthwise, poking out like pale green spokes among the purple and cream colored layers. So that’s how I cut them, with an inch or two of the stems attached. They looked beautiful and tasted wonderful but next time I probably won’t be including the stems- they were a bit tough.
But the bulbs…soft, mellow and dreamy 🙂
That’s how we learn, right? Use baby fennel if you’re lucky enough to find it! Just reserve the stems- mature or baby- for something else (They’re wonderful as a bed under salmon or chicken as it cooks).
Assembling Your Fennel & Sweet Potato Gratin
Your ingredients are prepped. Your oven is preheated. Now, we’re going to layer our ingredients in a casserole dish wide enough to hold everything in two overlapping layers. There’s no right or wrong way to arrange your vegetables. You can make circles from the outside in, you can move across in straight rows. Whatever makes you happy. Just do your best to keep the layers even so that you don’t have any areas that are much thicker than others because you want the whole thing to cook evenly.
Let’s put this lusciousness together!
- Place the fennel and sweet potatoes in a bowl with 1/4 cup of the cream. Sprinkle with some of the salt and pepper and work the vegetables and cream together with your hands so that the cream is thinly coating everything.
- Combine the remaining cream with the chopped garlic.
- Layer half of the vegetables, with edges overlapping, to cover the bottom of your dish
- Sprinkle with some salt and pepper, half of the thyme and chopped fennel fronds, and dot with half of the butter.
using creme brûlée and purple sweet potatoes and baby fennel 
using orange and creme brûlée sweet potatoes and mature fennel
- Drizzle with half of the cream/garlic mixture and sprinkle with 1/4 cup each of the shredded cheese.
- Repeat layers. You will have 1/4 cup of parmesan remaining. This will go on at the end to create that beautiful crust!
- Scrape any cream coating the vegetable bowl over the top of the gratin. Add some of the fennel fronds and grate fresh nutmeg over the top, if using.
Cooking Your Gratin
Once the gratin is assembled, cover it tightly with foil and bake for 45 minutes. Covering the dish is important because you are basically steaming the vegetables with the cream. Test after 45 minutes by inserting the tip of a sharp knife into the center of the gratin. The vegetables should be tender with barely any resistance. If they aren’t quite there yet, cook for another 10-15 minutes.
Uncover the gratin and top it with the remaining 1/4 cup parmesan. Place it in the oven UNCOVERED for another 15-20 minutes, until the top is golden and the vegetables are meltingly tender.
If it isn’t golden enough at this point you can put it under the broiler for a minute or so. Just watch carefully so it doesn’t burn! It happens quickly!
When the gratin is done make sure to let it stand for 10 minutes (or more). You want to give it just a little time to set up before digging in.
How Delicious Does This Look?!
Both of these gratins were wonderful! I wanted to see the color from the purple potatoes in the one on the left, so I didn’t add cheese at the end and ultimately sacrificed that golden crust. I guess that just reinforces how you can play around with recipes and do your own thing!
What To Serve With Fennel and Sweet Potato Gratin
Make this the star of your Meatless Monday and serve it with a green salad and/or simple blanched green beans
Or serve it as a side dish with:
- Lemony Pan Roasted Chicken
- Fall off the Bone BBQ Ribs
- Deboned Whole Chicken with Prosciutto, Spinach, Mushrooms and Gruyere
Whatever you do, just make it 🙂
Fennel & Sweet Potato Gratin
Ingredients
- 1 Tablespoon olive oil, for drizzling
- 1 1/2 Tbsp butter, softened
- 2 pounds assorted sweet potatoes, peeled and sliced thin (1/8th inch or thinner)
- 1 large fennel bulb, sliced thinly crosswise
- 1 1/4* cup heavy cream
- 3/4 cup shredded parmesan, divided
- 1/2 cup shredded gruyere
- 2 teaspoons chopped fresh thyme
- 1 Tbsp chopped fennel fronds plus additional unchopped fronds for garnish
- 2 garlic cloves, minced
- Kosher salt and cracked pepper to taste (I use about 1 1/2 teaspoons Diamond kosher and maybe 10 cranks of pepper)
- freshly grated nutmeg (optional)
Instructions
- Drizzle a little olive oil over casserole dish and brush evenly over bottom and sides. Alternatively you could use cooking spray, set aside. Preheat your oven to 375°f.
- Prep all of your ingredients, including putting your salt and pepper in a little bowl (it makes seasoning much easier when you're assembling the layers!)
- Place sweet potatoes and sliced fennel in a large bowl and pour 1/4 cup of the cream over them. Sprinkle with a little kosher salt and cracked pepper and work the vegetables and cream together with your hands until the cream is thinly coating all of the vegetables.
- Combine minced garlic with remaining cup of cream.
- Set 1/4 cup of the parmesan aside and combine the remaining parmesan and gruyere in a bowl.
- Arrange 1/2 of your vegetables with edges overlapping to cover the bottom of your casserole. Sprinkle with half of the thyme and chopped fennel fronds, 1/2 of the salt and pepper, 1/2 of the softened butter separated into little dabs with your fingers, 1/2 of the remaining cream and 1/2 of the combined cheeses. Repeat layers.
- If you have extra slices of vegetables try to find places to tuck them into your layers doing your best to keep everything level so it cooks evenly. Use a rubber spatula to scrape any remaining cream from the bowl onto the top of your gratin. Garnish with some of the fronds from the fennel. I also really like to grate some nutmeg over top at this point, but that's optional.
- Cover tightly with foil and bake 45 minutes. Test the center of the casserole with the tip of a sharp knife- the vegetables should be almost cooked through (tender with just a little resistance).If they seem at all hard, cover and cook another 10 minutes before proceeding.
- Once vegetables are tender, uncover, sprinkle with remaining 1/4 cup parmesan and continue cooking another 15-20 minutes until top is golden and vegetables are meltingly tender.
- If your top hasn't browned as much as you'd like place it under the broiler for a minute but watch very carefully and remove before it burns!
- Let it rest 10 minutes before serving and enjoy!
Notes
- Use more or less salt to your preference. My measurement is using Diamond Kosher salt, if you're using table salt or Mortons kosher salt you'll want to use less
- The nutmeg is optional but I really love what it adds here. I grate nutmeg over mine but you can use ground nutmeg. If you're using ground nutmeg a little goes a long way!
I’d love to hear how this turns out for you and if you change it up to make it your own! Reach out in the comments and let me know or tag me on Instagram or fb @breathingandcooking
Enjoy!
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