Here’s a hearty recipe from epicurious.com. If you happen to have an adjustable blade slicer, that will make quick work of slicing the turnips.
2 Tablespoons unsalted butter
2 ½ lb medium turnips, trimmed
1 Tablespoon chopped thyme
½ Tablespoon chopped savory
1 ½ teaspoons kosher salt
1/8 teaspoon cayenne
1 Cups heavy cream
1 Cups grated Parmigiano-Reggiano cheese
Preheat oven to 450° with rack in middle. Melt butter in ovenproof 12 inch heavy skillet, then cool.
Slice turnips paper-thin with slicer, then arrange one third of slices, overlapping tightly, in skillet, keeping remaining slices covered with dampened paper towels. Sprinkle with about 1/3 of thyme, savory, kosher salt, and cayenne. Make 2 more layers.
Cook, covered, over medium heat until underside is browned, about 10 minutes. Add cream and cook, covered, until center is tender—20-25 minutes.
Sprinkle evenly with cheese, then bake, uncovered, until golden and bubbling, 10-15 minutes. Let stand 5 minutes before serving.