The Best Root Vegetable Gratin Recipe
This root vegetable gratin is a perfect side dish that brings depth and coziness to any meal, and it’s a showstopper on holiday tables! My version, made with layers of colorful root veggies and an irresistible miso cream sauce, takes this gratin to a comfort food level of deliciousness. Topped with melted cheese and infused with earthy thyme, this gratin is the perfect blend of creamy, savory, and just a hint of warmth.
Why You’ll Love This Root Vegetable Gratin Recipe
This gratin doesn’t just look beautiful – it’s packed with flavor, thanks to a rich miso and cream sauce that brings out each of the root vegetable slices’ earthy, natural taste. Miso adds just the right amount of umami to complement the vegetables. This dish is simple to make and uses versatile ingredients, so you can work with whatever root vegetables you love or have on hand – potatoes, parsnips, carrots, and even fennel all work beautifully here. If you’re a fan of fall vegetables, you might also enjoy my roasted fall vegetables agrodolce, or my roasted vegetables with mint salsa verde. Both bring out the flavors of seasonal produce in a sweet-and-sour glaze.
To keep the flavors in this recipe balanced, I like to mix starchy and non-starchy vegetables, adding a little color where I can. Just be mindful of strong flavors like parsnip, which can sometimes overpower milder ingredients. And while the onion jam might feel like a small luxury, it adds a level of sweetness and depth that’s irresistible. This gratin is ideal for holiday side dishes alongside your turkey, but don’t be surprised if you’re tempted to make it for cozy weeknight dinners with some easy crispy chicken thighs, too!
What is Onion Jam?
Onion jam is a sweet, savory, and tangy condiment made by slowly cooking onions until caramelized and jam-like in texture, often with the addition of vinegar, sugar, and spices.
If you can’t find onion jam, you can easily make it at home by cooking onions low and slow with olive oil or butter, then adding a splash of vinegar and a touch of sweetener like honey or maple syrup. In a pinch, caramelized onions make a great substitute.
Ingredient Notes
- White miso paste: Adds a deep umami richness that enhances the earthy flavors of the root vegetables; if unavailable, you can substitute with a teaspoon of soy sauce or a touch of nutritional yeast for a hint of depth.
- Heavy cream: Creaminess binds the gratin together and creates a luscious texture; use cashew milk for a dairy-free option without sacrificing richness.
- Vegetable broth: Lightens the creamy base while adding extra savory flavor; any good-quality broth works here, even a mushroom broth if you want a hint of earthiness.
- Garlic cloves: If needed, you can use garlic powder, but fresh garlic is ideal for full flavor.
- Fresh thyme leaves: Thyme’s woodsy, aromatic notes complement the earthy root vegetables beautifully; rosemary or sage could be used sparingly if thyme isn’t available.
- Black pepper: Adds a subtle heat to balance the creamy elements; freshly ground pepper is best, but pre-ground will do in a pinch.
- Salt
- Ground nutmeg: A pinch of nutmeg brings warmth and depth, giving the gratin a subtle, cozy undertone; cinnamon or allspice would also work if you want to experiment.
- Onion jam: If you can’t find onion jam, slowly sauté diced onions until golden for a similar effect.
- Mixed root vegetables: Such as Russet potatoes, sweet potatoes, carrots, parsnips, celery root, rutabaga, fennel, etc. The heart of the gratin offers layers of flavor, color, and texture; try any mix you love, but make sure to cut thin slices for even cooking.
- Gruyère or Comté cheese: Feel free to get creative with different cheeses if desired.
- Olive oil: Helps create a golden, crisp topping and lightly coats the vegetables for added richness. Avocado oil is a good substitute.
See the full recipe card below for exact ingredient amounts and instructions.
Step-by-Step Instructions
Step 1: Preheat your oven to 375°F (190°C). In a medium saucepan, whisk together the white miso paste, heavy cream, vegetable broth, minced garlic, fresh thyme leaves, black pepper, a pinch of salt, and nutmeg. Heat this mixture over medium heat, stirring until the miso paste has completely dissolved and everything is well combined. Remove from heat and stir in the onion jam.
Step 2: In a large bowl, toss the thinly sliced root vegetables with the miso cream mixture. Make sure the vegetables are well coated.
Step 4: Grease a 13×9-inch baking dish with olive oil. Layer the coated root vegetables in the dish, slightly overlapping each slice as you go. Pour any remaining miso cream mixture over the top of the vegetables.
Step 5: Cover the entire dish tightly with aluminum foil and set it on a baking sheet. Bake in your preheated oven for 45 minutes.
Step 6: Carefully remove the foil and test the vegetables for tenderness by poking them with a paring knife. If they’re tender, you can pause the recipe here – let it sit at room temp for a couple of hours, and finish it after the turkey comes out of the oven.
Step 7: Sprinkle the shredded cheese over the top and return the casserole dish to the oven, baking for an additional 15 – 20 minutes until the cheese is melted and golden brown.
Step 8: Let the gratin cool slightly before serving. Garnish with fresh thyme leaves if you like, and season with salt to taste.
Tips for the Best Root Vegetable Gratin
- Keep the slices thin and uniform. For perfectly even slices, use a mandoline to cut your root vegetables. This ensures uniform thickness, which is key for even cooking and those beautiful, layered visuals that make gratins so irresistible. If you don’t have a mandoline, a sharp knife will work – just try to get slices about 1/8-inch thick.
- Use high-quality cheese. The cheese layer really shines here, so try to use Gruyère, Comté, or another high-quality option. The mild nuttiness and melting quality elevate the dish.
- Let the gratin rest. Allowing the gratin to cool slightly before serving helps the layers set, making it easier to serve and enhancing the flavors.
Make It Vegan
You’ll get a great result making this gratin vegan by substituting the heavy cream and cheese with dairy-free options. Cashew milk is a great swap for heavy cream – blend ½ cup raw cashew butter (or JOI cashew milk base) with 3 cups of water. Use your favorite vegan cheese for the topping.
Serving Tips
Here are some serving suggestions for your root vegetable gratin:
- Serve alongside my Thanksgiving salad with homemade pomegranate vinaigrette.
- The gratin’s creamy texture pairs so well with meat. Try pairing it with my grilled yogurt-marinated chicken kabobs or my turkey pot pie with biscuits.
- For a meatless meal, serve the gratin alongside hearty vegetarian dishes like my mushroom veggie chili.
- This gratin is a wonderful addition to holiday spreads. Pair it with my herb roasted spatchcocked turkey for a festive and satisfying meal.
- Try adding bacon, breadcrumbs, or nuts for some extra texture and flavor.
Storage Tips
Let the gratin cool, then cover it tightly or store it in an airtight container. Refrigerate for up to 3 days.
To freeze, bake until the vegetables are tender but skip the cheese topping. Cool completely, wrap tightly, and freeze for up to 1 month. To reheat, thaw the frozen gratin overnight in the fridge, top with cheese, and bake at 375°F (190°C) until warmed through and bubbly.
Recipe FAQs
Yes! You can bake the gratin up to the point of adding cheese, then refrigerate it once cooled. Reheat in the oven until warmed through, then add the cheese and finish baking until bubbly.
Feel free to add or swap in other root vegetables like turnips or beets, which will add a lovely color contrast and slight sweetness.
More Favorite Dishes
- Celery Root Puree
- Cozy Roasted Butternut Squash and Apple Soup
- Roasted Green Beans and Shallots with Lemon and Thyme
- Creamy Chicken and Wild Rice Soup
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The Best Root Vegetable Gratin
Ingredients
- ¼ cup white miso paste not low-sodium
- 1 ½ cups heavy cream or rich cashew milk
- 1 ½ cups vegetable or chicken broth
- 6 garlic cloves minced
- 2 Tablespoons fresh thyme leaves or 2 teaspoons dried thyme
- 1 teaspoon black pepper
- A big pinch of salt
- ¼ teaspoon ground nutmeg
- ¼ cup caramelized onion jam I used Divina or saute 1 onion, diced
- 4 pounds mixed root vegetables such as potatoes, sweet potatoes, carrots, parsnips, celery root, rutabaga, fennel, etc., sliced ⅛ -inch thick (THIN)
- 1-2 cups shredded Gruyere or Comte cheese
- Olive oil
- Salt to taste
Instructions
- Preheat your oven to 375°F (190°C).
- In a saucepan, whisk together the white miso paste, heavy cream, vegetable broth, minced garlic, thyme leaves, black pepper, a pinch of salt, and nutmeg. Heat the mixture over medium heat, stirring until the miso paste is fully dissolved and the ingredients are well combined. Remove the mixture from heat and stir in the onion jam..
- In a large mixing bowl, combine the thinly sliced root vegetables with the miso cream mixture. Make sure the vegetables are well coated.
- Grease 13 x 9 baking dish with olive oil. Layer the coated root vegetables in the dish, slightly overlapping the slices. Pour any remaining miso cream mixture over the top of the vegetables.
- Cover the baking dish with aluminum foil and place on a baking sheet. Bake in the preheated oven for about 45 minutes.
- Remove the foil and check to make sure the vegetables are tender by poking them with a paring knife. You can pause the recipe here, let it sit at room temp for a couple hours, and finish it after the turkey comes out of the oven. Sprinkle the shredded cheese over the top of the gratin and continue baking for an additional 15-20 minutes or until cheese is melted and lightly browned.
- Let the gratin cool slightly before serving. Garnish with fresh thyme leaves if desired and season with salt to taste.
Notes
- Keep the slices thin and uniform. For perfectly even slices, use a mandoline to cut your root vegetables. This ensures uniform thickness, which is key for even cooking and those beautiful, layered visuals that make gratins so irresistible. If you don’t have a mandoline, a sharp knife will work – just try to get slices about 1/8-inch thick.
- Use high-quality cheese. The cheese layer really shines here, so try to use Gruyère, Comté, or another high-quality option. The mild nuttiness and melting quality elevate the dish.
- Let the gratin rest. Allowing the gratin to cool slightly before serving helps the layers set, making it easier to serve and enhancing the flavors.
- Storage: Let the gratin cool, then cover it tightly or store it in an airtight container. Refrigerate for up to 3 days.
- To freeze, bake until the vegetables are tender but skip the cheese topping. Cool completely, wrap tightly, and freeze for up to 1 month. To reheat, thaw the frozen gratin overnight in the fridge, top with cheese, and bake at 375°F (190°C) until warmed through and bubbly.
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