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Cheesy Root Vegetable Gratin

Cheesy root vegetable gratin with thinly sliced Yukon gold, sweet potato, and parsnip, baked until fork-tender and topped with a bubbling Gruyere crust. French-inspired layering and a warmed cream-garlic bath create a creamy, golden finish.
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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: 540
Ingredients Equipment Method Notes

Ingredients
  

Cheesy Root Vegetable Gratin
  • 1 lb Yukon gold potatoes peeled and thinly sliced
  • 1 lb sweet potatoes peeled and thinly sliced
  • 2 parsnips peeled and thinly sliced
  • 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
  • 1 cup shredded Gruyere divided
  • 0.5 cup grated Parmesan

Equipment

  • 1 sheet pan

Method
 

Prep and heat the cream
  1. Preheat oven to 375°F and 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 (do not boil).
Layer and bake
  1. Layer a third of Yukon gold potatoes, sweet potatoes, and parsnips in the dish, then top with a third of shredded Gruyere.
  2. Repeat the layers twice, then pour the warm cream mixture evenly over the top so it seeps between slices.
  3. Cover with foil and bake for 45 minutes at 375°F.
  4. Uncover, sprinkle with grated Parmesan, and bake 20 to 25 minutes at 375°F until bubbly, golden, and fork-tender.
Rest and serve
  1. Rest for 10 minutes before serving so the gratin sets and slices cleanly.

Notes

For the creamiest texture, slice the vegetables thin and even so they bake at the same rate, and pour the steaming cream mixture over the full surface for consistent moisture. Refrigerate covered up to 4 days; reheat in a 350°F oven until hot throughout. Freezing is not recommended because potatoes and parsnips can turn grainy after thawing. Dietary swap: use lactose-free cream and milk for a lactose-free version (keep the same amounts).