Save to Pinterest This velvety sweet potato gratin brings together layers of thin-sliced sweet potatoes, a creamy Gruyère sauce, and the unexpected crunch of caramelized hazelnuts for a show-stopping side. With roots in classic French cooking, this dish feels special enough for a holiday yet works beautifully for cozy dinners. The savory richness and sweet nutty topping set it apart from the usual potato sides I grew up with and make it a true crowd-pleaser at any table.
I started making this for Thanksgiving years ago wanting a twist on gratin and cannot count the times people have begged for the recipe since. Even traditional eaters go back for seconds.
Ingredients
- Sweet potatoes sliced very thin: ensure melting tenderness with every bite so choose ones that are firm with smooth skins
- Yellow onion sliced fine: adds gentle depth beneath all the creamy layers
- Heavy cream and whole milk: together create a luscious sauce with classic richness aim for organic or local dairy if possible
- Gruyère cheese: brings nutty flavor and superb melt look for aged Gruyère or swap for Comté to vary the taste
- Unsalted butter: both greases the dish and adds flavor throughout use European-style butter for extra creaminess
- Garlic: fresh cloves give just the right aromatic lift make sure they are plump and not sprouting
- Fresh thyme leaves or dried: either infuses a subtle herbal backbone reach for fresh if you can
- Ground nutmeg: a pinch makes the whole gratin taste warm and special use freshly grated if you have it
- Salt and black pepper: season in layers to build depth
- Whole hazelnuts toasted and skinned: develop addictive crunch once caramelized look for raw nuts and toast them for best flavor
- Granulated sugar: is essential for making the caramel use fine white sugar for even melting
- Water: helps dissolve the sugar for caramelizing
- A pinch of salt: brings balance to the caramel and makes the hazelnut topping unforgettable
Instructions
- Preheat and Prep Butter the Dish:
- Preheat your oven to moderate heat. Grease your two-liter baking dish generously with butter to prevent sticking and boost flavor.
- Infuse the Cream:
- In a saucepan, bring together cream, milk, minced garlic, thyme, nutmeg, salt, and pepper. Warm gently over low heat until steaming but not bubbling. Allow the flavors to infuse while avoiding scorching the milk.
- Layer the Vegetables:
- Arrange half of the sweet potato slices evenly over the bottom of the dish making sure the edges overlap for a luxurious texture. Scatter half the sliced onions over this layer then add about a third of the Gruyère cheese to start building creaminess. Repeat with the remaining sweet potatoes and onions to create beautiful stacked layers.
- Pour and Top:
- Carefully pour the infused cream mixture across all layers making sure it seeps through each crevice. Sprinkle on the remaining Gruyère cheese for a golden, bubbly finish. Dot the surface with pieces of butter distributing them for even richness.
- Bake Covered and Uncovered:
- Cover the dish tightly with foil and bake for over half an hour allowing the potatoes to steam and soften. Remove the foil and continue baking to finish cooking and achieve a deep golden crust on top. Watch the last several minutes so it does not brown too quickly.
- Prepare Caramelized Hazelnuts:
- Line a tray with parchment so your caramelized nuts will not stick. In a small saucepan combine sugar and water over medium heat stirring until dissolved then stop stirring. Let the mixture bubble until it turns a rich amber color. Immediately add toasted hazelnuts and a pinch of salt stirring quickly to coat. Work fast and pour out onto the tray separating nuts before they set into clumps.
- Finish and Serve:
- When the gratin has finished baking and the topping is deeply golden let it cool briefly before topping with a generous handful of rough chopped caramelized hazelnuts. Serve warm for the best balance of creamy and crunchy textures.
Save to Pinterest The hazelnuts are my secret obsession in this recipe. I learned from my grandmother to always toast nuts before caramelizing them which makes the flavor pop. The crunch on top is now my kids’ favorite part and I sometimes double it for extra bites to snack on.
Storage Tips
Store leftovers tightly wrapped in the fridge for up to three days. The gratin reheats beautifully covered in a moderate oven or as single portions in the microwave. If freezing allow the dish to cool completely then wrap well in foil and freeze for up to one month. Thaw overnight in the fridge before reheating in the oven to preserve creaminess.
Ingredient Substitutions
Switch Gruyère for Comté or an aged cheddar for a more robust cheese taste. For a vegan spin use a combination of coconut cream and your favorite plant-based cheese plus vegan butter. No hazelnuts on hand Pecans or walnuts also toast and caramelize gorgeously though the flavor will shift slightly.
Serving Suggestions
Pair this gratin with roasted chicken or pork for a comfort-forward meal. It shines next to other holiday classics and is hearty enough to stand alone as a main for vegetarians. Top with fresh thyme or parsley for a splash of green before serving.
Cultural and Historical Context
French gratins are a centuries-old staple revered for their comforting layers of creamy potatoes and cheese. This sweet potato version updates tradition by adding caramelized nuts which are often found in regional European winter desserts. If you love the elegance of French cuisine but crave something new this dish bridges classic and modern.
Seasonal Adaptations
Swap sweet potatoes for a mix of winter squash or add slices of purple potato for extra color in the colder months Stir in a tablespoon of finely chopped sage for a Thanksgiving twist In spring lighten the dish by adding thinly sliced leeks or fennel bulb with the onions
Success Stories
After introducing this at a Friendsgiving it became a yearly tradition with friends texting for the recipe every November. One neighbor made it for a bridal shower and declared it the only dish to be scraped completely clean. Even kids who usually turn up their noses at sweet potatoes are now gratin converts in my house.
Freezer Meal Conversion
Make the gratin ahead but stop before baking. Wrap well and freeze. When ready to serve thaw in the fridge overnight and bake as directed adding extra time if still cold in the center. Top with fresh caramelized hazelnuts just before serving for best crunch.
Save to Pinterest Serve this gratin straight from the oven to showcase the beautiful golden top and sweet nutty aroma. Each bite promises comfort and a surprising crunch your guests will remember.
Common Recipe Questions
- → Can I prepare this in advance?
Yes, you can assemble the gratin ahead and refrigerate it unbaked. Allow to come to room temperature before baking for best results.
- → What are good substitutes for Gruyère?
Comté or sharp cheddar offer a similar melt and flavor profile if Gruyère isn't available.
- → How can I make this dish vegan?
Use coconut cream and plant-based cheese, and replace butter with a vegan alternative to suit a vegan diet.
- → Do I need a mandoline slicer?
A mandoline ensures even, thin slices but a sharp knife works well if used carefully for consistent results.
- → Are there allergens I should be aware of?
This side contains dairy and hazelnuts. It is naturally gluten-free but check labels on all products used.