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Cheesy Root Vegetable Gratin

Cheesy root vegetable gratin layers thin-sliced potatoes, parsnip, carrot, and turnip baked until tender with a golden, bubbling Gruyère-Parmesan crust. A classic French-American style baked gratin made creamy with a garlic-thyme cream mixture.
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Prep Time 25 minutes
Cook Time 1 hour
Total Time 1 hour 25 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: French-American
Calories: 650
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 cloves garlic 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
  • 0.25 tsp salt to taste
  • 0.25 tsp pepper to taste

Equipment

  • 1 sheet pan
  • 1 baking dish

Method
 

Prep and build the gratin
  1. Preheat the oven to 375F and butter a 9x13 baking dish generously.
  2. Whisk heavy cream, whole milk, garlic, fresh thyme, nutmeg, salt, and pepper until fully combined.
  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 and press down gently so the liquid settles between layers.
Bake and finish
  1. Cover tightly with foil and bake 40 minutes at 375F.
  2. Uncover and scatter Gruyere cheese and parmesan over the top.
  3. Bake 20-25 more minutes at 375F until the vegetables are completely tender and the top is golden and bubbly.
Rest and serve
  1. Rest the gratin 10 minutes before serving.

Notes

For the cleanest tender layers, slice all roots to a similar thickness (about 1/8 inch). Refrigerate leftovers in an airtight container for up to 3 days; reheat covered at 325F until hot. Freezing is not ideal due to cream texture, but you can freeze unbaked assembled gratin (up to 1 month) and bake from foil at 375F, adding extra time if needed. Dairy-light swap: replace heavy cream + milk with an equal amount of lactose-free cream and lactose-free milk for similar flavor and bake behavior.