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Cheesy Root Vegetable Gratin

Cheesy root vegetable gratin with thin-sliced Yukon gold potatoes, sweet potatoes, and parsnips baked until bubbly and golden under a Gruyère crust. Finished with Parmesan and a short rest for creamy, fork-tender layers.
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Prep Time 25 minutes
Cook Time 1 hour 10 minutes
resting 10 minutes
Total Time 1 hour 45 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: French-inspired
Calories: 590
Ingredients Equipment Method Notes

Ingredients
  

Yukon gold potatoes
  • 1 lb Yukon gold potatoes, peeled and thinly sliced
sweet potatoes
  • 1 lb sweet potatoes, peeled and thinly sliced
parsnips
  • 2 parsnips, peeled and thinly sliced
cream mixture
  • 1.5 cup heavy cream
  • 0.5 cup whole milk
  • 3 garlic, minced
  • 1 tsp fresh thyme leaves
  • 1.5 tsp salt
  • 0.5 tsp black pepper
  • 0.25 tsp nutmeg
cheeses
  • 2 cup shredded Gruyere divided
  • 0.5 cup grated Parmesan

Equipment

  • 1 sheet pan
  • 1 Dutch oven

Method
 

Prep and preheat
  1. Preheat oven to 375F, then butter a 9x13-inch baking dish. The dish should be evenly coated so the top browns without sticking.
Warm the cream mixture
  1. Warm heavy cream, whole milk, minced garlic, thyme leaves, salt, black pepper, and nutmeg over heat until steaming, then remove from heat. Look for steam rising from the pot and small bubbles at the edges.
Layer and sauce
  1. Layer a third of the sliced Yukon gold potatoes, sweet potatoes, and parsnips in the baking dish, then top with a third of the shredded Gruyere. You should see distinct layers with cheese sprinkled on top.
  2. Repeat the layers twice so the vegetables are divided evenly through three rounds. Keep the slices relatively uniform so they bake tender at the same rate.
  3. Pour the warm cream mixture evenly over the top. The liquid should settle between slices and come close to the surface.
Bake
  1. Cover with foil and bake 45 minutes at 375F. The vegetables should soften and the dish should look steamy beneath the foil.
  2. Uncover, sprinkle grated Parmesan over the top, and bake 20-25 minutes at 375F until bubbly, golden, and fork-tender. Watch for active bubbling and browned edges across the surface.
Rest and serve
  1. Rest the gratin 10 minutes before serving. It will thicken slightly so the layers hold together when you scoop.

Notes

For the creamiest texture, keep the vegetable slices thin and consistent so they soften evenly without needing extra bake time. Refrigerate leftovers in a covered container for up to 3 days; reheat covered in a 325F oven until hot through. Freezing is not recommended because the dairy can break after thawing. For a lighter version, replace heavy cream with half-and-half and expect a slightly less rich, more delicate set.