Cheesy Root Vegetable Gratin is a comforting dish full of tender, thinly sliced root veggies like potatoes, carrots, and parsnips, all baked together under a golden, bubbly layer of melted cheese. The creamy sauce soaks into the veggies, making every bite rich and flavorful without being too heavy.
I love making this gratin especially during colder months when I want something warm and soothing on the table. What’s great about this recipe is how easy it is to customize with whatever root vegetables you have on hand. I usually add a bit of garlic and fresh thyme to give it a lovely little boost that makes the whole house smell amazing while it’s cooking.
My favorite way to serve this is alongside a simple green salad or roasted chicken. It’s a dish that feels special but really isn’t much trouble at all, which makes it perfect for both weeknights and dinner parties. Every time I bring it out, people ask for the recipe because it’s so good and feels like a cozy hug on a plate.
Key Ingredients & Substitutions
Potatoes and Root Veggies: I like using a mix of potatoes, sweet potatoes, carrots, and parsnips for a range of flavors and textures. If you can’t find parsnips, turnips or rutabagas work well too.
Cream and Milk: Heavy cream makes the gratin rich and creamy, but you can use half-and-half or whole milk for a lighter version. Just expect it to be a bit less thick.
Cheese: Gruyère adds a wonderful nutty flavor and melts nicely. Parmesan mixed in boosts sharpness. Mozzarella can be a milder substitute, or for a dairy-free option, try a plant-based cheese that melts.
Herbs and Seasoning: Fresh thyme is my favorite here. If you don’t have fresh, dried thyme works well too. A pinch of nutmeg is optional but adds a subtle warmth I enjoy.
How Do I Get Thin, Evenly Cooked Vegetable Slices?
Uniform slices ensure even cooking and a beautiful dish. Here’s how to nail it:
- Use a sharp knife or a mandoline slicer for consistent thin slices. I prefer a mandoline for speed and uniformity.
- Slice all vegetables to roughly the same thickness, about 1/8 inch.
- If using a mandoline, be cautious and use the hand guard for safety.
- Arrange slices tightly in overlapping rows to help them cook evenly and hold the creamy sauce.
These simple steps help your gratin cook evenly and look lovely on the table every time.
Equipment You’ll Need
- Mandoline slicer or sharp knife – I recommend a mandoline for quick, uniform slices that cook evenly.
- 9×13 inch baking dish – perfect size for all those layered veggies to fit nice and snug.
- Saucepan – to heat the cream mixture and infuse the flavors.
- Measuring cups and spoons – for the cream, milk, and seasonings.
- Cheese grater – so you can easily grate the Gruyère (or cheese of your choice).
- Pastry brush or small spoon – to butter the dish before layering.
Flavor Variations & Add-Ins
- Swap Gruyère for sharp cheddar or fontina for different cheesy flavors and meltiness.
- Add cooked bacon or pancetta between layers for a smoky, savory twist.
- Mix in sautéed onions or leeks to add sweetness and aromatics.
- Sprinkle with fresh herbs like parsley or thyme on top before serving for a fresh note.
Cheesy Root Vegetable Gratin
Ingredients You’ll Need:
Vegetables:
- 3 large potatoes, peeled and thinly sliced
- 2 large sweet potatoes, peeled and thinly sliced
- 2 large carrots, peeled and thinly sliced
- 1 large parsnip, peeled and thinly sliced
For the Cream Mixture:
- 3 cloves garlic, minced
- 2 cups heavy cream
- 1 cup whole milk
- 2 tsp fresh thyme leaves (or 1 tsp dried thyme)
- Salt and freshly ground black pepper, to taste
- Optional: pinch of nutmeg
Other:
- 1 ½ cups grated Gruyère cheese (or a mix of Gruyère and Parmesan)
- 2 tbsp unsalted butter, for greasing the dish
How Much Time Will You Need?
This dish takes about 15 minutes to prepare, including slicing the vegetables and making the cream mixture. Then, it bakes covered for 45 minutes, followed by about 20-25 minutes uncovered to brown the top. Finally, allow 10 minutes to rest before serving. Overall, plan for roughly 1 hour and 30 minutes from start to finish.
Step-by-Step Instructions:
1. Get Ready:
Preheat your oven to 375°F (190°C). Generously butter a 9×13 inch baking dish so the vegetables won’t stick and the gratin gets nice and golden on the edges.
2. Warm the Creamy Sauce:
In a saucepan, combine the heavy cream, milk, minced garlic, thyme, salt, pepper, and a pinch of nutmeg if you like. Warm this mixture over medium heat until it just starts to simmer, then turn off the heat and set it aside.
3. Layer the Vegetables:
Arrange the thin veggie slices in the baking dish. Try to overlap each slice just a little and alternate the different colors and types of root vegetables to create a pretty pattern.
4. Pour & Add Cheese:
Pour the warm cream mixture evenly over the veggies. Then sprinkle the grated Gruyère (or your cheese blend) generously on top.
5. Bake Covered & Then Uncovered:
Cover the dish loosely with aluminum foil and bake for 45 minutes. After that, remove the foil and bake for another 20-25 minutes to brown and bubble up the cheese, and to make sure the veggies are tender when poked with a fork.
6. Let It Rest:
Once it’s out of the oven, let the gratin sit for about 10 minutes before serving. This rest time helps the sauce thicken up a bit, making it even creamier and easier to serve.
Can I Use Frozen Vegetables for This Gratin?
It’s best to use fresh root vegetables because frozen ones may release extra water, making the gratin watery. If you must use frozen, thaw them completely and pat dry before slicing and layering.
Can I Make This Gratin Ahead of Time?
Yes! Assemble the gratin up to the baking step, cover it tightly, and refrigerate for up to 24 hours. When ready, bake as directed, adding a few extra minutes if needed since it will be cold going into the oven.
How Should I Store Leftovers?
Keep leftovers in an airtight container in the fridge for up to 3 days. Reheat gently in the oven or microwave until warmed through.
What Cheese Can I Substitute if I Don’t Have Gruyère?
You can swap Gruyère for other melty cheeses like fontina, mozzarella, or sharp cheddar. Mixing in a bit of Parmesan adds nice flavor if you like a cheesier top.