The mix of red, white, and sweet potatoes with onions and fennel and a variety of cheeses make for a nutty, rich, and herbal side dish with garlic that is fit for a King, Queen – or a whole Royal Family.
So, a couple weeks ago I started playing with it to fine tune my vision and streamline the steps of this recipe. My first instinct was to caramelize the onions and fennel before mixing them in with the cream, but I actually found that by the time the whole thing baked for an hour an a half, the onions and fennel cooked down way too much and were almost indistinguishable. I also originally planned to peel the potatoes, or maybe just the sweet potatoes, but after trying the recipe both ways, peeling just seemed like an unnecessary extra step.
I figured that everyone, including myself, would appreciate any unnecessary steps that I could eliminate. Enough effort goes into slicing everything with the mandoline and arranging the slices in tight circles, so as long as it still tastes great, why not make everything else super easy?
Speaking of slicing everything with a mandoline, please be careful when you’re slicing. Those pesky mandolines have bitten me a few times, but if you go slow and use a guard when you get toward the end of the potato, I promise that you can keep your fingertips intact. Another option to keep your fingers super safe would be to invest in a cut resistant glove. Whenever I’ve had any accidents with mandolines though, it’s been because I was going too fast or was distracted by something else in the kitchen. The blades are sharp and deserve your undivided attention, so please use caution! Unfortunately this recipe will be kind of difficult to perfect without one. Sorry friends!
I mean, if you have surgically precise knife skills, by all means please go ahead and just use a knife, but it’s really important that all the slices are the exact same thickness so everything cooks at the same time.
Let me tell you friends, this recipe was worth the wait and the effort. Who could say no to tender, delicate, richly flavored potatoes with crunchy, crispy top edges? The mix of red, white, and sweet potatoes is wonderfully wintery without being too sweet, and the onions and fennel caramelize in the oven and their flavors go from pungent and intense to rich, mellow, and slightly sweet. The mix of cheeses adds a salty, nutty richness, and the sage, thyme, and garlic make this dish the perfect side to any winter meal.
Step by Step Guide to Making Fennel and Sweet Potato Gratin
Prep Oven and Cheeses:
- Preheat oven to 400°F. Mix comte and parmesan cheeses, setting aside 1/3 for topping. In the larger cheese portion, mix in cream, salt, pepper, garlic, sage, and thyme.
- Slice potatoes, fennel, and onions using a mandoline for even thickness. Combine in a large bowl.
Combine with Cream Mixture:
- Toss vegetables with cream and cheese mixture, ensuring each slice is coated.
Prepare Baking Dish:
- Butter a large casserole dish or 12″ cast iron skillet. Neatly stack potato, onion, and fennel slices in the dish vertically.
- Cover and bake for 30 minutes. Uncover and bake for another 30 minutes. Sprinkle with reserved cheese and bake until golden brown, about 30 minutes more.
Rest and Serve:
- Let the gratin rest for at least 15 minutes before serving.
- Cheese Choice: The nutty flavor of Comte or Gruyere adds depth.
- Mandoline Use: Ensure uniform thickness for even cooking.
- Seasoning: Don’t shy away from the salt; it’s crucial for flavoring this hearty dish.
- Resting Time: Allows the gratin to set and flavors to meld.
Tux is a food blogger, photographer, dog lover, husband, and avid baker living in Bushwick, Brooklyn. Originally from upstate New York, he inherited his love of cooking and baking from his mother and grandmother. With the encouragement of good friends and several glasses of wine, he began his food writing and blogging adventure in the fall of 2013. Learn more about Tux at his blog Brooklyn Homemaker