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Cheesy Root Vegetable Gratin

Cheesy root vegetable gratin with thinly sliced Yukon gold potatoes, sweet potatoes, and parsnips baked until fork-tender under a bubbling golden Gruyère crust. A warm garlic-thyme cream mixture keeps every layer creamy and sliceable.
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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: 520
Ingredients Equipment Method Notes

Ingredients
  

Vegetables
  • 1 lb Yukon gold potatoes peeled and thinly sliced
  • 1 lb sweet potatoes peeled and thinly sliced
  • 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
Cheese
  • 2 cup shredded Gruyere divided
  • 0.5 cup grated Parmesan

Equipment

  • 1 sheet pan

Method
 

Prep and preheat
  1. Preheat the oven to 375F, then butter a 9x13-inch baking dish. Set the dish aside while you warm the cream.
Warm the cream
  1. Warm heavy cream, whole milk, garlic, fresh thyme leaves, salt, black pepper, and nutmeg over low heat until steaming. Remove from the heat once the mixture is steaming but not boiling.
Layer the gratin
  1. Layer a third of the Yukon gold potatoes, sweet potatoes, and parsnips in the baking dish. Top with a third of the shredded Gruyere.
  2. Repeat the layers twice with the remaining vegetables and shredded Gruyere. Pour the warm cream mixture evenly over the top so it settles between slices.
Bake and finish
  1. Cover with foil and bake at 375F for 45 minutes. The vegetables should be starting to soften and the edges should look slightly set.
  2. Uncover, sprinkle with grated Parmesan, and bake for 20-25 minutes at 375F. Bake until the top is bubbly, golden, and the vegetables are fork-tender.
Rest and serve
  1. Rest the gratin for 10 minutes before serving. This helps the creamy layers set so you can slice cleanly.

Notes

Pro tip: keep the vegetable slices as thin and even as possible so they cook at the same rate and produce a tender, creamy texture throughout. Refrigerate leftovers in an airtight container for up to 4 days; reheat covered in a 325F oven until warmed through. Freezing is not recommended for best texture because the potatoes can turn mealy after thawing. For a lighter option, use half-and-half instead of heavy cream (texture stays creamy, but it won’t be as rich).