Ingredients
Scale
For the Crust:
- 2 tablespoons unsalted butter
- 1 large yellow onion, thinly sliced
- 2 cloves garlic, minced
- 1 1/2 cups heavy cream
- 1/2 cup whole milk
- 2 tablespoons fresh thyme, minced
- 1/4 teaspoon freshly grated nutmeg
- 1 1/2 teaspoons salt
- 1/2 teaspoon black pepper
- 2 pounds root vegetables, peeled and thinly sliced (we used 1/2 pound each of sweet potato, parsnip, celery root, and Yukon gold potato)
- 1 cup Gruyère cheese, shredded
- 1/2 cup Parmesan cheese, shredded
Instructions
1. Prepare the Crust:
- Preheat oven to 375˚F. Lightly grease a 9″x13″ baking dish and set aside.
- Melt butter in a medium saucepan over medium heat. Add onions and sauté for 5 to 7 minutes until soft and translucent. Add garlic and sauté for another 2 minutes.
- Pour in heavy cream and milk and bring to a simmer. Stir in thyme, nutmeg, salt and pepper and remove from heat.
- Arrange 1/3 of the root vegetables into the bottom of the prepared baking dish. Pour 1/3 of the cream mixture over the vegetables and top with 1/3 of the Gruyère and Parmesan cheeses.
- Repeat step 4 two more times, ending with the cheeses.
- Cover with foil and bake for 40 minutes. Uncover and bake for another 20 to 25 minutes or until the top is golden brown and the vegetables are tender.
- Remove from oven and allow gratin to rest for 10 minutes before serving.
Notes
You can use any combination of root vegetables for this recipe. We used a combination of sweet potato, parsnip, celery root and Yukon gold potato, but feel free to use your favorites!