The perfect Thanksgiving side!
1 tablespoon unsalted butter
2 cups heavy cream
3 garlic cloves (peeled, minced)
1 small shallot (peeled, minced)
1/2 teaspoon freshly grated nutmeg
1 1/2 teaspoon Kosher salt
1/2 teaspoon freshly ground black pepper
1 3/4 cups Parmigiano-Reggiano (freshly grated)
1 pound red beets (peeled and sliced 1/16-inch thick on a mandoline)
1 pound sweet potatoes (peeled and sliced 1/16-inch thick on a mandoline)
1 pound Yukon Gold potatoes (peeled and sliced 1/16-inch thick on a mandoline)
1 pound turnips (peeled and sliced 1/16-inch thick on a mandoline)

Preheat oven to 375ºF. Lightly butter a 9×13-inch baking dish.
In a medium bowl, add the cream with the garlic, shallot, nutmeg, salt and pepper and whisk to combine. Add the 1 cup of the grated cheese and stir to combine.
In a large bowl, add the beets and toss with 1/4 of the cream mixture. Arrange the beets in the baking dish in an even layer, overlapping them slightly. Pour any remaining cream from the bowl over the beets. Repeat this process with the sweet potatoes, Yukon Gold potatoes and turnips, using 1/3 of the remaining cream mixture for each vegetable. Press a sheet of parchment paper on top of the turnips, then cover the dish tightly with foil.
Bake the gratin for about 1 hour and 30 minutes, or the vegetables are tender. Uncover and top with the remaining 3/4 cup of the cheese. Bake for about 15 minutes longer, until golden brown. Transfer the gratin to a baking rack and allow to cool for at least 15 minutes before serving.
Tip: Hold the potatoes in water while slicing the remaining vegetables so they do not oxidize and turn a brown color.