If you can't decide between mashed potatoes or sweet potato casserole, this double potato gratin combines both into one amazing dish. Yukon gold potatoes and sweet potato slices are layered with spices, covered in heavy cream and topped with a buttery breadcrumbs and parmesan cheese. It is important that the potato slices are roughly the same thickness. The best way to do this is with a mandoline or the slicing attachment for your food processor. This rich potato dish will be a favorite on the Thanksgiving table.
Double Potato Gratin
3/4 teaspoon freshly ground nutmeg
2 teaspoons kosher salt
1/2 teaspoon freshly ground black pepper
3 sprigs fresh thyme, leaves removed
3 large Yukon Gold potatoes, peeled and thinly sliced
3 large sweet potatoes, peeled and thinly sliced
1 cup heavy whipping cream
1/2 cup half and half
1/2 cup milk
3/4 cup panko breadcrumbs (Japanese breadcrumbs)
1/2 cup parmesan cheese, shredded
3 tablespoons unsalted butter, melted
Step 1: Preheat oven to 350 degrees Fahrenheit. Grease a 2½ quart baking dish with olive oil or butter.
Step 2: Mix nutmeg, thyme leaves, salt, and pepper in a small bowl. Place a layer of Yukon Gold potatoes in the baking dish. Sprinkle he spice mixture over the top of the potatoes and then add another layer of sweet potatoes. Continue to alternate the two kinds of potatoes with the spice mixture.
Step 3: Combine the heavy whipping cream, milk and half and half in a bowl with a spout. Pour the milk mixture over the potatoes on the potatoes, making sure each slice is covered. Cover the baking dish tightly with foil and bake for 1 hour and 15 minutes or until potatoes are tender.
Step 4: Mix panko breadcrumbs, parmesan cheese and melted butter together in a bowl until breadcrumbs are moistened. Evenly sprinkle the breadcrumb mixture over the top of the cooked potatoes and place the potatoes back in the oven for 3 to 5 minutes or until the top is golden brown. Let cool for 5 to 10 minutes before serving.