My favorite Root Vegetable Gratin Recipe

I first put this Root Veggie Gratin together for our Thanksgiving dinner; I was in search of something more fun and nutrient-dense than a basic mashed potato. I've been tweaking the recipe a bit since then and think I've found the perfect balance! This recipe makes a fairly large batch... but I actually like it a lot better the second and third day, reheated in the oven. And for all of you starting your Sugarfreed 14 days soon, YES it's an approved recipe!

Root Vegetable Gratin

(makes 4-6 servings)


1 large sweet potato

1 celery root, peeled top removed

1 large turnip

1 large rutabaga

1 medium golden beet

1 medium bulb fennel

1 large leek

3 Tablespoons grass-fed butter or ghee

1 tablespoon fresh garlic, minced

1 tablespoon fresh thyme, finely diced

1 cup chicken broth (plus a little more, if needed)

1 to 1 1/2 cups heavy cream

8-10 ounces of Gruyere cheese, shredded

1 teaspoon sea salt

1 teaspoon cracked black pepper



  • Preheat the oven to 350 degrees, and have ready a large glass or ceramic baking dish. (I've used a large rectangular 10x14", or alternately two small oval LaCruset dishes.)
  • Slice the sweet potato, celery root, rutabaga, turnip, and beet into large, thin rounds. If you have a mandolin slicer, it can really help you make uniform thin slices about 1 mm thick. Another trick is to cut the veggie in half first so you have a flat edge to lay it on, to assist you in slicing. Place them all in the largest mixing bowl you have. Set aside.
  • Heat 3 tablespoons butter in a large cast-iron skillet over medium high. While it's heating, slice the leek and fennel into thin strips. Saute the leek and fennel together in the cast iron, stirring frequently, for about 5 minutes. Add the diced garlic and saute for 1 minute more.
  • Turn the heat to low, then add 1 cup of broth, and 1 cup of heavy cream. Add the thyme, and salt & pepper. Stir the mix together for about 2 minutes, being careful to keep it well below a boil... you just want the flavors to start to mix together with the leeks/garlic/fennel.
  • Remove from heat, and very carefully, pour the cream mix into the bowl over the sliced root veggies. (My cast iron is huge and there's NO chance of me lifting it successfully with stuff in it, so I ladle the cream mix over the veggies until I can pour the rest out!) Using a large wooden spoon, gently toss the veggies into cream mix to coat.
  • Add the shredded Gruyere to the mix and toss gently again.
  • I think this next step is easiest using your hands; layer the coated veggies into your baking dish, spreading out and pressing down as you go to make sure all the slices fit in and stack well, and watching to distribute the cheese evenly.
  • At this point, you'll have to eyeball the mix and notice if you might want to add a little more broth or cream, according to how big the veggies were, and how juicy you like the gratin! If there was no cream/broth left in the bottom of the mixing bowl, consider topping off with a little more of each, once they're in the baking dish.
  • NOTE: you may want to place the baking dish on top of a sheet pan if it's especially full with the root veggies... it can bubble over and cause an oven mess! Bake for 45 to 60 minutes. Look for the cheese to be bubbly and golden brown on top. For me it's usually closer to the 60 minutes to get to that point... but check yours at 45 minutes, as oven temps vary.

The Root Veggie Gratin will easily store for a few days in the fridge, and reheats beautifully in the oven at 350 for about 10-15 minutes!


xo January