Cheesy Sweet Potato Gratin (Printable Version)
Comforting gratin featuring layers of sweet potatoes, golden onions, and creamy cheeses baked beautifully.
# What You Need:
→ Vegetables
01 - 2 lbs sweet potatoes, peeled and thinly sliced
02 - 2 large yellow onions, thinly sliced
03 - 2 cloves garlic, minced
→ Dairy & Cheese
04 - 2 cups shredded Gruyère cheese
05 - 1 cup shredded sharp cheddar cheese
06 - 1 1/2 cups heavy cream
07 - 1/2 cup whole milk
08 - 3 tbsp unsalted butter
→ Seasonings
09 - 1/2 tsp dried thyme
10 - 1/2 tsp ground black pepper
11 - 1/2 tsp salt plus additional to taste
12 - 1/4 tsp ground nutmeg
→ Optional
13 - 1 tbsp gluten-free or all-purpose flour
14 - 2 tbsp chopped fresh chives for garnish
# How to Make It:
01 - Preheat oven to 375°F. Generously grease a 9x13-inch baking dish with butter or cooking spray.
02 - Melt 2 tbsp butter in a large skillet over medium heat. Add sliced onions and a pinch of salt. Cook, stirring frequently, until onions are deeply golden and caramelized, about 20-25 minutes. Add minced garlic during the final minute and remove from heat.
03 - Combine cream, milk, thyme, nutmeg, black pepper, and remaining 1 tbsp butter in a small saucepan over medium-low heat. Heat until steaming but not boiling. If using flour, whisk in until smooth and slightly thickened.
04 - Arrange half the sweet potato slices in the prepared dish, slightly overlapping. Season lightly with salt. Spread half the caramelized onions over potatoes, then sprinkle with half the Gruyère and half the cheddar cheese.
05 - Repeat layering with remaining sweet potatoes, caramelized onions, and cheeses.
06 - Pour the warm cream mixture evenly over the layered ingredients, ensuring coverage across the entire dish.
07 - Cover baking dish tightly with aluminum foil. Bake for 40 minutes to allow potatoes to steam and soften.
08 - Remove foil and continue baking uncovered for 20 minutes, or until the top is golden brown and bubbly, and potatoes are fork-tender.
09 - Allow gratin to rest for 10 minutes before serving to set. Garnish with chopped fresh chives if desired.
# Expert Tips:
01 -
- The combination of Gruyère and sharp cheddar creates this incredibly complex flavor that feels fancy but comes together with simple ingredients you can grab anywhere
- Unlike heavy creamed spinach dishes, this actually gets better after sitting in the fridge overnight, making it the ultimate make-ahead side for stress-free entertaining
02 -
- If you rush the onion caramelization step you will end up with bitter tasting onions instead of sweet ones, so give them the full 20 minutes they need
- Letting the gratin rest for at least 10 minutes after baking is crucial because the sauce needs time to thicken slightly or it will run everywhere when you serve it
03 -
- A mandoline slicer creates perfectly even potato slices that cook uniformly, but if you are using a knife, take your time to keep slices as consistent as possible
- Grating your own cheese instead of buying pre-shredded makes a huge difference because the anti-caking agents in packaged cheese prevent smooth melting