3 pounds sweet potatoes, peeled and sliced into 1/8 inch rounds
1/4 cup unsalted butter
3 cloves garlic, finely minced
1/4 cup all-purpose flour
1 1/2 cups whole milk
1 cup heavy cream
1 teaspoon salt
1/2 teaspoon black pepper
1/2 teaspoon dried thyme
1/4 teaspoon ground nutmeg
1 1/2 cups shredded Gruyere or sharp white cheddar cheese
1/2 teaspoon smoked paprika for garnish
Instructions
Preheat your oven to 375 degrees Fahrenheit. Lightly grease a 9 by 13 inch baking dish with butter or a small amount of oil to ensure the potatoes do not stick to the sides during the baking process.
Peel the sweet potatoes and use a sharp knife or a mandoline slicer to create uniform rounds about 1/8 inch thick. Keeping the slices consistent in thickness ensures that all the potatoes cook through at the same rate, avoiding any firm bites in the finished dish.
In a medium saucepan, melt the butter over medium heat. Add the minced garlic and cook for about one minute until fragrant. Whisk in the flour to create a roux, cooking for another minute. Slowly pour in the milk and heavy cream while whisking constantly to prevent lumps. Stir in the salt, pepper, thyme, and nutmeg. Continue to cook until the sauce thickens enough to coat the back of a spoon.
Place half of the sliced sweet potatoes in the prepared baking dish, overlapping them slightly in even rows. Pour half of the cream sauce over the potatoes and sprinkle with half of the shredded cheese. Repeat the layers with the remaining potatoes, sauce, and cheese.
Cover the dish tightly with aluminum foil and bake for 40 minutes. Remove the foil and continue baking for another 20 minutes, or until the potatoes are tender when pierced with a fork and the cheese on top is bubbly and golden brown. Let the dish rest for 10 minutes before serving to allow the sauce to set.
