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Cheesy Root Vegetable Gratin

Cheesy root vegetable gratin with thinly sliced potatoes, parsnips, carrots, and turnips baked until tender in a creamy garlic-thyme sauce. Finished with a golden, bubbly Gruyère and parmesan crust for a classic French-inspired bake.
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Prep Time 25 minutes
Cook Time 1 hour
Resting 10 minutes
Total Time 1 hour 35 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: French-American
Calories: 520
Ingredients Equipment Method Notes

Ingredients
  

Cheesy root vegetable gratin base
  • 2 lb Yukon gold potatoes peeled and thinly sliced
  • 2 parsnips medium, peeled and thinly sliced
  • 3 carrots peeled and thinly sliced
  • 1 turnip or celery root large, peeled and thinly sliced
  • 4 garlic cloves, minced
  • 2 cup heavy cream
  • 1 cup whole milk
  • 2 tsp fresh thyme
  • 0.25 tsp nutmeg
  • 2 cup Gruyere cheese shredded
  • 0.5 cup parmesan grated
  • 3 tbsp unsalted butter
  • 1 salt to taste
  • 1 pepper to taste

Equipment

  • 1 sheet pan

Method
 

Prep and assemble
  1. Preheat the oven to 375F, then butter a 9x13 baking dish generously.
  2. Whisk heavy cream, whole milk, garlic, fresh thyme, nutmeg, 1 teaspoon salt, and pepper together until smooth.
  3. Layer Yukon gold potatoes, parsnips, carrots, and turnip or celery root in the dish, alternating types in slightly overlapping rows.
  4. Pour the cream mixture over the vegetables, then press down gently so the slices settle.
Bake and finish
  1. Cover tightly with foil and bake for 40 minutes at 375F until the edges look slightly softened.
  2. Uncover the dish and scatter Gruyere cheese and parmesan over the top.
  3. Bake uncovered for 20-25 minutes at 375F until the vegetables are completely tender and the top is golden and bubbly.
  4. Rest the gratin for 10 minutes before serving so the creamy layers set.

Notes

For clean, even slices (and faster tender-cooking), aim for consistently thin layers when slicing Yukon gold potatoes, parsnips, carrots, and turnip or celery root. Refrigerate leftovers in a covered container for up to 4 days and reheat in a 325F oven until warmed through. Freezing is not recommended because the cream can break and the texture may turn grainy after thawing. If you want a lighter option, use half-and-half instead of heavy cream and keep the same baking times.