Introduction

This Cheesy Root Vegetable Gratin is a comforting and flavorful dish that highlights a medley of tender, thinly sliced root vegetables smothered in a rich, creamy cheese sauce. It’s perfect as a hearty side for holiday meals or cozy dinners any time of the year.

This image shows a baked vegetable gratin dish in an oval pan with golden handles, placed on a white marbled surface with two vintage silver spoons nearby and a beige cloth on the side. The gratin is arranged in five layers of thinly sliced vegetables: starting from the top, the first layer is light yellow potatoes with a crispy brown edge, followed by a dark purple layer of eggplant slices, then bright orange sweet potatoes, a second light yellow potato layer, and finally more sweet potatoes at the bottom. Each layer is evenly stacked with the edges slightly browned and sprinkled with small green herb leaves. The dish has a golden, cheesy crust with a textured bubbly look on top. photo taken with an iphone --ar 4:5 --v 7

Ingredients

2 pounds (about 900g) mixed root vegetables (potatoes, sweet potatoes, parsnips, carrots), peeled and thinly sliced
1 small onion, thinly sliced
2 cloves garlic, minced
2 tablespoons butter
2 tablespoons all-purpose flour
2 cups milk (whole or 2%)
1 1/2 cups shredded sharp cheddar cheese, divided
1/2 cup grated Parmesan cheese, divided
Salt and black pepper to taste
1/4 teaspoon ground nutmeg (optional)
Fresh thyme leaves (optional, for garnish)

Instructions

Step 1: Preheat your oven to 375°F (190°C). Grease a 9×13 inch baking dish with butter or cooking spray to prevent sticking.
Step 2: Peel and thinly slice the mixed root vegetables using a knife or mandoline slicer for even thickness. Place the sliced vegetables in a large bowl.
Step 3: In a medium saucepan, melt 2 tablespoons of butter over medium heat. Add the sliced onion and minced garlic, sautéing for 3-4 minutes until the onion is translucent and fragrant.
Step 4: Sprinkle the flour over the sautéed onion and garlic and stir constantly for 1-2 minutes to form a roux. Gradually pour in the milk while stirring continuously. Cook for 5-7 minutes until the sauce thickens. Reduce heat to low and stir in 1 cup shredded cheddar and 1/4 cup grated Parmesan until melted and smooth. Season with salt, black pepper, and nutmeg if using.
Step 5: Pour the cheese sauce over the sliced root vegetables in the bowl, gently tossing to coat evenly.
Step 6: Transfer the coated vegetables to the prepared baking dish, arranging them evenly in a single layer.
Step 7: Cover the dish tightly with aluminum foil and bake for 35-40 minutes, or until the vegetables are tender when pierced with a fork.
Step 8: Remove the foil and sprinkle the remaining 1/2 cup shredded cheddar cheese and 1/4 cup grated Parmesan evenly over the top.
Step 9: Return the uncovered dish to the oven and bake an additional 15-20 minutes until the top is golden brown and bubbly. Garnish with fresh thyme leaves if desired.
Step 10: Let the gratin cool for a few minutes before serving. Enjoy warm as a savory, cheesy side dish.

Tips & Variations

Use a mandoline slicer to ensure uniform vegetable slices for even cooking.
Substitute or add root vegetables like turnips or rutabaga for different flavors.
The nutmeg is optional but adds a warm, subtle depth to the cheese sauce.
For a richer sauce, use whole milk; for a lighter version, choose 2% milk.
This dish can be assembled a day ahead and baked just before serving.

Storage

Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in the oven at 350°F (175°C) until warmed through to maintain the best texture and flavor.

How to Serve

The dish is a baked vegetable gratin arranged in an oval white dish with golden handles. It has four rows of thinly sliced vegetables, each row a different color and texture. Starting from the top, there is a row of golden yellow slices with a slightly crispy browned edge, followed by a row of dark purple slices that look soft and tender with some shine. The next row is composed of bright orange slices with caramelized edges, and the final row at the bottom is a mix of pale yellow slices with browned spots. All rows are sprinkled with fresh green herbs and small bits of melted cheese on top. The dish rests on a white marbled surface next to two vintage silver spoons and a folded light brown cloth. photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I use other types of cheese for this gratin?

Yes, you can substitute cheddar and Parmesan with other melting cheeses like Gruyère or mozzarella for a different flavor profile.

Is it necessary to cover the gratin while baking?

Covering the gratin during the initial baking step ensures the vegetables cook evenly and retain moisture. Removing the cover later helps brown and crisp the cheesy topping.