100-Layer Root Vegetable Gratin Recipe

3 types of cheese take this bubbly casserole to the next level

Well, if you really want to get picky, this gratin may not have exactly 100 layers. It does, however, pile thin slices of parsnips, potatoes, celery root, sweet potatoes and turnips to make a vegetable casserole sure to impress. And even if you're not a big fan of vegetables, three kinds of cheese and a rich cream sauce will probably convert you.

You'll want to slice the vegetables right before you are about to assemble the dish. Often,  recipes will instruct you to hold your root vegetables in water to prevent them from oxidizing and turning brown, but be sure not to do that for this recipe. Dropping the vegetables into water will wash away the starches you need to thicken the cream into a rich sauce that bonds the vegetables together.

Check out some of our favorite vegetarian recipes.

Recipe from the Tasting Table Test Kitchen

100-Layer Root Vegetable Gratin
5 from 48 ratings
Five types of root vegetables and three kinds of cheese make for the richest gratin.
Prep Time
Cook Time
to 10 servings
Total time: 1 hour, 20 minutes
  • 1 tablespoon unsalted butter
  • 1 cup coarsely grated Gruyère cheese
  • 1 cup coarsely grated Comté cheese
  • 1 cup coarsely grated Parmesan cheese
  • 1½ pounds (4 large) parsnips, thinly sliced on a mandoline
  • 1 tablespoon, plus 2½ teaspoons, kosher salt, divided
  • 1½ pounds (1 large) celery root, thinly sliced on a mandoline
  • 1 pound (3 medium) sweet potatoes, thinly sliced on a mandoline
  • 1 pound (2 medium) white turnips, thinly sliced on a mandoline
  • 1½ pounds (3 medium) Yukon Gold potatoes, thinly sliced on a mandoline
  • 3 cups heavy cream
  • 1 tablespoon thyme leaves
  • 2 garlic cloves, finely grated
  • Freshly ground black pepper, to taste
  • 1 cup (4 ounces) coarse sourdough bread crumbs
  • 2 tablespoons roughly chopped parsley, plus more for garnish
  • 2 tablespoons roughly chopped sage, plus more for garnish
  • 1 tablespoon olive oil
  • Pinch red pepper flakes
  1. Preheat the oven to 400º and grease a 9-by-13-inch baking dish with the butter. In a small bowl, toss the cheeses together and set aside.
  2. In the greased baking dish, layer the parsnips in overlapping layers to cover the dish. Season with ½ teaspoon of kosher salt and scatter ½ cup of the cheese mixture over top. Continue this process of layering, seasoning and scattering ½ cup of the cheese mixture with the celery root, sweet potatoes and turnips. Layer the Yukon Gold potatoes last and season with the remaining ½ teaspoon salt. Do not top with any cheese.
  3. In a small pan, combine the cream with the remaining 1 tablespoon of salt, the thyme leaves, garlic and black pepper. Bring to a simmer over medium-high heat, then remove from the heat and pour into the dish over the vegetables. Place a piece of parchment directly over the vegetables and bake until the vegetables are tender when pierced with a paring knife, 45 to 50 minutes.
  4. Meanwhile, in a small bowl, toss the bread crumbs with the parsley, sage, olive oil and pepper flakes. Remove the baking dish from the oven and discard the parchment. Scatter the remaining 1 cup of grated cheese over the vegetables, followed by the bread crumb mixture. Return to the oven and bake until golden brown, 15 to 20 minutes more.
  5. Remove from the oven and let cool for 20 minutes before cutting. Garnish with more parsley and sage, then serve.
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