2 tablespoons butter, divided
1 1/2 pounds turnips, thinly sliced into rounds
1 teaspoon Kosher salt
Freshly ground black pepper
1 cup Gruyere cheese, grated
2 cups milk
1/2 cup cream
1 garlic clove, minced
1 tablespoon fresh oregano leaves, chopped
2 teaspoons fresh thyme leaves, chopped
One pinch ground Cayenne pepper
One pinch nutmeg
1/4 cup Parmigiano-Reggiano, grated
2 tablespoons fresh parsley leaves, chopped
Heat the oven to 400°F. Rub half of the butter on a 2-quart baking or gratin dish.
Place the sliced turnips in a bowl and season with the salt and a generous grind of pepper. Layer the slices around the gratin dish.
In a bowl, add half of the Gruyere, milk, cream, garlic, oregano, thyme, cayenne and nutmeg. Whisk to combine. Pour over the turnips in the dish. Sprinkle the remaining Gruyere on top. Chop the remaining butter, and put that on top, too.
Transfer the dish to the oven and bake for 45 minutes. Remove it from the oven, sprinkle the Parmigiano-Reggiano on top and return the dish to the oven. Bake another 15 to 20 minutes, until the turnips are soft and the cheese is browned on top. Remove from the oven and garnish with the parsley.