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Cheesy Root Vegetable Gratin

Cheesy root vegetable gratin with thin-sliced Yukon gold, sweet potato, and parsnip layered and baked until fork-tender under a bubbly golden Gruyère crust. Warm cream infused with garlic and thyme so every slice is creamy and evenly seasoned.
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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: 690
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 and milk
  • 1.5 cup heavy cream
  • 0.5 cup whole milk
Aromatics and seasonings
  • 3 clove 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 Parmesan Grated

Equipment

  • 1 sheet pan

Method
 

Prep and preheat
  1. Preheat oven to 375°F, then butter a 9x13-inch baking dish.
  2. Warm heavy cream, whole milk, garlic, fresh thyme leaves, salt, black pepper, and nutmeg until steaming, then remove from heat.
Layer and bake
  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.
  2. Repeat the layers two more times, then pour the warm cream mixture evenly over the top.
  3. Cover with foil and bake for 45 minutes at 375°F, until the vegetables start to soften.
Finish and rest
  1. Uncover, sprinkle Parmesan over the top, and bake 20-25 minutes until bubbly, golden, and fork-tender.
  2. Rest the gratin for 10 minutes before serving, so the sauce thickens slightly and slices hold together.

Notes

To keep the gratin creamy and sliceable, aim for uniformly thin vegetable slices so they cook at the same rate. Store covered in the refrigerator up to 3 days; reheat in a 350°F oven until hot through. Freeze is not recommended for the best creamy texture. For a lighter option, substitute half-and-half for heavy cream, keeping the bake time the same.