Cheesy Sweet Potato Gratin (Printable)

Baked layers of sliced sweet potatoes, caramelized onions, and melted cheese in a creamy blend.

# What You'll 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 more to taste)
12 - 1/4 tsp ground nutmeg

→ Optional

13 - 1 tbsp gluten-free flour or all-purpose flour for thickening
14 - 2 tbsp chopped fresh chives for garnish

# Directions:

01 - Preheat your oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - In a large skillet over medium heat, melt 2 tbsp butter. 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 and cook for 1 minute more. Remove from heat.
03 - In a small saucepan, combine heavy cream, whole milk, dried thyme, ground nutmeg, black pepper, and remaining 1 tbsp butter. Heat over medium-low heat until steaming, but do not boil. If using flour, whisk it in until smooth to slightly thicken the mixture.
04 - Arrange half of the sweet potato slices in the prepared baking dish, overlapping slightly. Season lightly with salt.
05 - Spread half of the caramelized onions evenly over the potatoes. Sprinkle with half of the Gruyère cheese and half of the cheddar cheese.
06 - Repeat layering with remaining sweet potato slices, followed by remaining caramelized onions, and the rest of the Gruyère and cheddar cheeses.
07 - Pour the warm cream mixture evenly over the layered ingredients, ensuring it reaches all corners of the dish.
08 - Cover the baking dish tightly with aluminum foil. Bake for 40 minutes to allow potatoes to cook through.
09 - Remove the foil and continue baking uncovered for an additional 20 minutes, or until the top is golden brown and bubbly, and the potatoes are fork-tender.
10 - Let the gratin rest for 10 minutes before serving to allow the layers to set. Garnish with fresh chives if desired.

# Expert Advice:

01 -
  • The sweet and savory play between caramelized onions and sharp cheddar creates this incredible depth that nobody expects from a potato dish
  • It makes you look like you spent hours fussing over details when really you just layered things and let the oven do the heavy lifting
  • The leftovers, if you somehow have any, reheat beautifully for lunch the next day
02 -
  • Patience with the onions makes or breaks this dish because rushed onions taste merely cooked, not transformed
  • A mandoline creates perfectly even slices, but if you are cutting by hand just try to keep the thickness consistent
03 -
  • Use the shredded cheese from a block rather than pre shredded bags because the coating on pre shredded cheese prevents it from melting smoothly
  • If the cream looks like it might bubble over during baking, place the baking dish on a sheet pan to catch any drips

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