Description

A comforting and flavorful Cheesy Root Vegetable Gratin featuring layers of sweet potatoes, parsnips, and beets baked in a rich cream sauce with Parmesan, Gruyère, garlic, and fresh thyme. This dish is perfect as a hearty side or vegetarian main course, offering a delicious blend of earthy roots and creamy, cheesy goodness with a golden crust.

Ingredients

Scale

Vegetables

1–2 long sweet potatoes (about 2 inches thick), peeled
3–4 large parsnips, ends trimmed and peeled
3–5 small beets, peeled

Dairy & Cheese

1 tablespoon unsalted butter, softened
14 tablespoons heavy cream, divided (whole milk can be used but will be less creamy)
4 ounces grated Parmesan, divided
1 ounce shredded Gruyère

Herbs & Seasonings

1 tablespoon fresh minced thyme, divided plus more for garnish
1 garlic clove, minced
Salt and pepper to taste

Instructions

Preheat and Prepare Baking Dish: Preheat your oven to 375°F (190°C). Butter a medium-sized gratin or baking dish with the softened unsalted butter to prevent sticking and add flavor.
Slice the Vegetables: Using a sharp knife or mandoline, slice the peeled sweet potatoes, parsnips, and beets into uniform thin rounds, about 1/8 to 1/4 inch thick. This ensures even cooking and layering.
Make the Cream Sauce: In a mixing bowl, combine 12 tablespoons of heavy cream, 3 ounces of grated Parmesan, minced garlic, half of the fresh thyme, and season with salt and pepper. Mix well to create a flavorful creamy sauce.
Layer the Vegetables: Arrange a layer of sweet potato slices evenly on the bottom of the buttered dish. Follow with a layer of parsnips, then beets, overlapping slightly. Sprinkle a portion of the remaining Parmesan and some thyme between layers, then drizzle portions of the cream sauce over each layer. Repeat until all vegetables and sauce are used, finishing with vegetables on top.
Top and Bake: Pour the remaining 2 tablespoons of heavy cream over the top layer of vegetables. Sprinkle the shredded Gruyère and the remaining grated Parmesan evenly over the surface for a golden cheesy crust. Bake uncovered in the oven for about 45-55 minutes, or until the vegetables are tender and the top is bubbling and browned.
Garnish and Serve: Remove from the oven and let the gratin rest for 5-10 minutes to set. Garnish with additional fresh thyme before serving. Serve warm as a savory side dish or a vegetarian entrée.

Notes

Whole milk can substitute heavy cream but expect a thinner sauce and less creaminess.
Use a mandoline slicer for uniform vegetable slices to ensure even cooking.
Beets may bleed color; lining layers or using parchment paper can help avoid mixing colors.
Leftovers can be refrigerated and gently reheated in the oven to maintain texture.
For a gluten-free version, ensure cheeses and ingredients are certified gluten-free.

Keywords: root vegetable gratin, sweet potato gratin, parsnip gratin, beet gratin, cheesy gratin, baked root vegetables, vegetarian gratin, comfort food