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Cheesy Root Vegetable Gratin

Cheesy root vegetable gratin with thinly sliced potato, parsnip, carrot, and turnip baked until tender and golden-bubbly under a Gruyere-Parmesan crust. Creamy garlic-thyme sauce soaks into every layer for a sliceable, richly set bake.
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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: 630
Ingredients Equipment Method Notes

Ingredients
  

Potatoes
  • 2 lb Yukon gold potatoes peeled and thinly sliced
Parsnips
  • 2 parsnips medium, peeled and thinly sliced
Carrots
  • 3 carrots peeled and thinly sliced
Turnip or celery root
  • 1 turnip or celery root large, peeled and thinly sliced
Garlic and herbs
  • 4 garlic cloves minced
  • 2 tsp fresh thyme
  • 0.25 tsp nutmeg
Dairy base
  • 2 cup heavy cream
  • 1 cup whole milk
Cheese
  • 2 cup Gruyere cheese shredded
  • 0.5 cup parmesan grated
Butter and seasoning
  • 3 tbsp unsalted butter
  • 0.25 salt to taste
  • 0.25 black pepper to taste

Equipment

  • 1 sheet pan

Method
 

Prep and preheat
  1. Preheat the oven to 375°F, then generously butter a 9x13 baking dish.
  2. Whisk the heavy cream, whole milk, minced garlic, fresh thyme, nutmeg, 1 teaspoon salt, and pepper until smooth.
Layer and bake covered
  1. Layer the root vegetables in the dish, alternating types in slightly overlapping rows.
  2. Pour the cream mixture over the vegetables and press down gently to help the layers settle.
  3. Cover tightly with foil and bake for 40 minutes at 375°F.
Add cheese and finish
  1. Uncover and scatter the Gruyere and parmesan evenly over the top.
  2. Bake 20 to 25 minutes more at 375°F until the vegetables are completely tender and the top is golden and bubbly.
Rest
  1. Rest for 10 minutes before serving to let the gratin set slightly for clean slices.

Notes

Pro tip: slice the vegetables evenly (about the same thickness) so they finish tender at the same time. Refrigerate leftovers in an airtight container for up to 4 days; reheat covered at 350°F until hot through. Freezing is not ideal because the cream sauce can separate after thawing. Dietary swap: for a lighter version, use half-and-half instead of heavy cream (texture will be slightly less rich).