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Cheesy Root Vegetable Gratin

Layers of tender root vegetables baked in rich, creamy cheese sauce creating the ultimate comfort food side dish perfect for holidays.
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Prep Time 30 minutes
Cook Time 1 hour 20 minutes
Total Time 1 hour 50 minutes
Servings: 8 servings
Course: Main Course, Side Dish
Cuisine: Comfort Food, French
Calories: 420
Ingredients Equipment Method Notes

Ingredients
  

Vegetable Base
  • 2 large sweet potatoes peeled and sliced
  • 3 medium russet potatoes peeled and sliced
  • 3 large carrots peeled and sliced
  • 2 large parsnips peeled and sliced
  • 2 tbsp olive oil
  • 1 tsp salt
  • 0.5 tsp black pepper
Cheese Sauce
  • 4 tbsp unsalted butter
  • 4 tbsp all-purpose flour
  • 2 cups heavy cream
  • 1 cup whole milk
  • 1.5 cups aged cheddar cheese grated
  • 1 cup Gruyère cheese grated
  • 1 tsp salt
  • 0.5 tsp white pepper
  • 0.25 tsp nutmeg
Assembly
  • 2 tbsp fresh thyme leaves
  • 0.5 cup additional cheddar cheese for topping
  • 2 tbsp fresh parsley chopped for garnish

Equipment

  • 9x13 inch baking dish
  • Large saucepan
  • Baking sheets
  • Sharp knife or mandoline

Method
 

  1. Preheat oven to 375°F (190°C) and generously butter a 9x13-inch baking dish.
  2. Prepare all vegetables by washing, peeling, and slicing them to uniform thickness using a sharp knife or mandoline.
  3. Toss sliced vegetables with olive oil, salt, and pepper in a large bowl, ensuring even coating.
  4. Arrange vegetables on baking sheets in single layers and roast for 15 minutes until slightly tender.
  5. Melt butter in large saucepan over medium heat, then whisk in flour to create smooth roux.
  6. Gradually add cream and milk, whisking constantly, cook until mixture thickens to coat spoon.
  7. Remove from heat and stir in both cheeses until melted, season with salt, white pepper, and nutmeg.
  8. Layer half the roasted vegetables in prepared baking dish, overlapping in attractive pattern.
  9. Pour half the cheese sauce over vegetables, spread evenly, sprinkle with half the thyme.
  10. Repeat layering with remaining vegetables and cheese sauce, creating overlapping patterns.
  11. Top with additional cheddar cheese and remaining thyme, cover with foil and bake 45 minutes.
  12. Remove foil and bake 15-20 minutes more until golden brown and bubbling around edges.
  13. Let rest 10 minutes before serving to allow layers to set properly.

Notes

Can be assembled a day ahead and refrigerated before final baking. Add 10-15 minutes to cooking time if baking from cold. Store leftovers up to 4 days in refrigerator.