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Cheesy Root Vegetable Gratin

Cheesy root vegetable gratin made French-style with thinly sliced potatoes, parsnips, carrots, and turnip baked until tender in a garlic thyme cream bath. Finished with a golden, bubbling Gruyère and Parmesan crust for a rich, sliceable side dish.
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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: 650
Ingredients Equipment Method Notes

Ingredients
  

potatoes
  • 2 lb Yukon gold potatoes
parsnips
  • 2 parsnips
carrots
  • 3 carrots
turnip or celery root
  • 1 turnip or celery root
garlic
  • 4 garlic cloves
cream and milk
  • 2 cup heavy cream
  • 1 cup whole milk
thyme and nutmeg
  • 2 tsp fresh thyme
  • 0.25 tsp nutmeg
cheeses
  • 2 cup Gruyere cheese
  • 0.5 cup parmesan
butter
  • 3 tbsp unsalted butter
seasoning
  • salt and pepper to taste

Equipment

  • 1 sheet pan

Method
 

Prep and heat
  1. Preheat the oven to 375°F, then butter a 9x13 baking dish generously with unsalted butter.
Make the cream mixture
  1. Whisk heavy cream, whole milk, garlic, fresh thyme, nutmeg, salt and pepper together until smooth and evenly combined.
Layer and bake
  1. Layer Yukon gold potatoes, parsnips, carrots, and turnip or celery root in the dish, alternating types in slightly overlapping rows.
  2. Pour the cream mixture over the vegetables and press down gently so the liquid seeps between the slices.
  3. Cover tightly with foil and bake for 40 minutes, until the vegetables have started to soften.
  4. Uncover the dish, scatter Gruyère cheese and parmesan over the top, and bake for 20 to 25 more minutes until the top is golden and bubbly and the vegetables are completely tender.
Rest
  1. Rest the gratin for 10 minutes before serving, so the layers set and slice cleanly.

Notes

Pro tip: Slice the root vegetables very thin and fairly even so they cook through at the same rate without hard centers. Refrigerate leftovers in an airtight container for up to 4 days; reheat covered in a 325°F oven until hot. Freezing isn’t recommended because the cream can separate when thawed. For a lighter option, swap part of the heavy cream with additional whole milk, but expect a slightly less rich set.