We genuinely enjoy cooking. But when it comes time for our family to divide Thanksgiving duties, we somehow always get stuck with sweet potatoes. Which would be fine — except that few people at our holiday table particularly enjoy eating them; especially not when they’re dotted with a sugar slick of mini marshmallows. That’s why, each year, we take great pains to devise exciting, totally adult preparations for sweet potatoes, and one of our favorite inventions thus far is this utterly elegant Gratin — layer upon layer of orange yams, earthy sage, and nutty Gruyere cheese. Believe us, this tasty dish will make acolytes of even the most hardened sweet potato naysayers!
Sweet Potato and Gruyere Gratin
2 tablespoons of olive oil
1 large onion, cut in half and thinly sliced
1 cup of whipping cream
1½ tablespoons of minced garlic
1 cup of milk
Salt and pepper to taste
1/8 teaspoon of ground nutmeg
5 to 6 large sweet potatoes
½ cup of grape seed oil
½ cup of fresh sage leaves
2 cups of breadcrumbs
1½ cups of shredded Gruyere cheese (divided)
Preheat oven to 375 degrees. Heat oil in a heavy-bottom pan over medium heat. Add onion and reduce heat to medium-low. Caramelize onions until golden brown, stirring frequently, about 10 to 15 minutes, and set aside.
In a medium saucepan, bring cream, minced garlic, milk, salt, pepper and nutmeg to a boil and set aside. Using a food processor or mandolin, peel and slice sweet potatoes thin, and place in water to prevent browning. Place grapeseed oil and sage leaves in a food processor, and process until well blended. Strain into a small bowl, mix with the breadcrumbs and ½ cup of the Gruyere, and set aside.
Butter an 8-by-8-inch baking dish. Drain sweet potatoes, and place one-fifth of the sweet potato slices in the bottom of the baking dish. Top with half of the caramelized onions. Add another layer of sweet potatoes, then ½ cup of the remaining Gruyere cheese. Add another layer of sweet potatoes, then the remaining onions. Add another layer of sweet potatoes, then the remaining ½ cup of Gruyere, and the final layer of sweet potatoes. Evenly pour the cream over the entire casserole. Top with the sage-breadcrumb mixture, and cover the pan with tinfoil.
Bake for about one hour, or until the potatoes are tender. Serve warm.