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Cheesy Root Vegetable Gratin

Cheesy root vegetable gratin with thinly sliced Yukon gold potato, sweet potato, and parsnip baked in a creamy garlic-cream base, topped with a golden Gruyère crust. Layers stay tender and fork-ready while the cheese bubbles and browns under foil then uncovered.
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Prep Time 25 minutes
Cook Time 1 hour 10 minutes
Total Time 1 hour 35 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: French-inspired
Calories: 610
Ingredients Equipment Method Notes

Ingredients
  

Cheesy root vegetable gratin components
  • 1 lb Yukon gold potatoes
  • 1 lb sweet potatoes
  • 2 parsnips
  • 1.5 cup heavy cream
  • 0.5 cup whole milk
  • 3 garlic
  • 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 Parmesan

Equipment

  • 1 sheet pan

Method
 

Prep and preheat
  1. Preheat the oven to 375°F, and butter a 9x13-inch baking dish so the gratin releases easily.
  2. Warm the heavy cream, whole milk, garlic, thyme leaves, salt, black pepper, and nutmeg over heat until steaming, then remove from the heat.
Layer and sauce
  1. Layer one-third of the sliced Yukon gold potatoes, sweet potatoes, and parsnips in the baking dish.
  2. Top the vegetables with one-third of the shredded Gruyere, forming an even cheesy layer.
  3. Repeat the layers twice with the remaining vegetables and another one-third of shredded Gruyere each time.
  4. Pour the warm cream mixture evenly over the top so the layers bake creamy.
Bake and finish
  1. Cover the dish with foil and bake for 45 minutes, until the vegetables are just beginning to soften.
  2. Uncover, sprinkle with the grated Parmesan, and bake 20 to 25 minutes more until bubbly, golden, and fork-tender with browned cheese at the edges.
  3. Rest the gratin for 10 minutes before serving, letting the cream set for cleaner slices.

Notes

For the creamiest texture, slice the potatoes and parsnips thin and uniform so they cook at the same rate. Store leftovers covered in the refrigerator up to 4 days; reheat in a 325°F oven until warmed through. Freezing is not recommended because the cream can break when thawed. To make it lighter, use half-and-half instead of heavy cream (the bake will be slightly less rich but still creamy).