Chef John's Root Vegetable Gratin
A hearty and elegant gratin of thinly sliced root vegetables — potatoes, turnip, rutabaga, celery root, and parsnip — baked in a savory cream sauce and topped with Parmigiano-Reggiano until golden and bubbling.
Ingredients
- *2 medium Yukon Gold potatoes, scrubbed and sliced 1/8-inch thick with peel
- *1 turnip, peeled and sliced 1/8-inch thick
- *1 rutabaga, peeled and sliced 1/8-inch thick
- *1 small celery root, peeled and sliced 1/8-inch thick
- *1 parsnip, peeled and sliced 1/8-inch thick
- *Salt, to taste
- *3 cloves garlic, minced
- *2 tablespoons butter
- *1 1/4 cups chicken broth
- *1 cup heavy cream
- *1 tablespoon chopped fresh thyme
- *1 pinch ground nutmeg
- *1 pinch cayenne pepper
- *2 teaspoons olive oil
- *1/4 cup finely grated Parmigiano-Reggiano cheese, divided
Instructions
- 1
Preheat the oven to 375 degrees F (190 degrees C).
- 2
Bring a large pot of generously salted water to a boil. Add the sliced vegetables and cook uncovered for 3 minutes. Drain in a colander, then immediately immerse in ice water for several minutes until cold to stop the cooking process. Once the vegetables are cold, drain well and set aside.
- 3
Cook garlic and butter in a large skillet over medium heat until the garlic starts sizzling, about 3 minutes.
- 4
Stir in chicken broth, heavy cream, thyme, nutmeg, and cayenne pepper. Cook until the mixture begins to simmer, about 5 minutes.
- 5
Coat a 9x13-inch baking dish with olive oil and spread the parboiled vegetables evenly over the oil.
- 6
Pour the broth and cream mixture over the vegetables and top with half of the grated Parmigiano-Reggiano cheese.
- 7
Cover the baking dish loosely with aluminum foil, place on a baking sheet, and bake in the preheated oven for 40 minutes.
- 8
Remove the baking dish from the oven and top with the remaining Parmigiano-Reggiano. Bake uncovered until the vegetables are browned, bubbling, and tender, about an additional 30 minutes.
- 9
Remove from the oven and let rest for 20 minutes before serving. Note: root vegetable sizes vary — you'll need enough to fill a 9x13-inch casserole dish about 3/4 full.