Turnip and Sweet Potato Gratin

The holidays are all about the side dishes—sorry, turkey. This sweet potato and turnip recipe is a hearty, nutritious, and cheesy casserole and it's the perfect addition to your holiday table. It's a delicious cheesy gratin that's made a little differently to the typical gratin recipe. Turnips and sweet potatoes stand in for the usual white potatoes. Additionally, instead of submerging the vegetables in a cream mixture, they are sprinkled with flour, which slowly thickens the chicken broth as it bakes. 

It tastes much more cozy and decadent than you might expect—there’s plenty of nutty cheese on top for good measure. Whether you’re hosting a festive dinner or you’ve been tasked with bringing a side dish, this recipe is a great one.

Gratin vs. Scalloped Potatoes

Gratins and scalloped potatoes are similar in terms of flavor, appearance, and technique. The difference comes down to dairy. Scalloped potatoes can be considered an Americanized version of potatoes au gratin. A gratin is typically thickened without a roux and topped with lots of melty cheese. Instead, the American dish is made by baking the potatoes in a pool of cream sauce with a roux. Each is decadent in its own right, and it’s really just a matter of preference. 

Though we call this turnip and sweet potato dish it's made a little differently from a traditional gratin. It’s more like a cross between scalloped potatoes and potatoes au gratin. The liquid in the dish is thickened with flour (rather than a technical roux), though that liquid is not dairy-based. Chicken broth and white wine are what create the sauce.

Ingredient Substitutions

This recipe is very versatile. Many of the ingredients can be swapped for others that you already have on hand, and others can be substituted if you don’t particularly love them. 

• Root vegetables: Turnips and sweet potatoes are two of our favorite root vegetables. Sweet potatoes have a sugary sweet flavor, while turnips are more nutty and earthy so they make a great pairing. You can add or swap in any other root vegetables that you like, including white potatoes, rutabaga, parsnips, large carrots, celeriac, and beets. 
• Chicken broth: Chicken broth adds a lot of flavor to this dish, but a good-quality vegetable stock makes the dish vegetarian-friendly. If you made a turkey for the big day and have some homemade turkey stock available, put it to good use in this recipe (in addition to your gravy, of course). 
• White wine: If you don’t have white wine, simply add more broth along with a splash of something acidic, such as fresh lemon juice or apple cider vinegar. 
• Gruyère cheese: Any other nutty, fragrant cheese will work in place of Gruyère. Try something like Swiss, aged gouda, or a sharp white cheddar instead.