Lunch: Root Vegetable Gratin

Recipe by /contributors/alison-roman The key to gratins is having all the ingredients—whether they're basic potatoes or the mixed root vegetables below—sliced the same thickness so they cook at the same rate. Make friends with a mandoline: It quickly yie

Ingredients

4 tablespoons unsalted butter, divided, plus more for baking dish
1 1/2 cups coarse fresh breadcrumbs
1 1/2 cups grated Parmesan, divided
6 sprigs thyme plus 1 tablespoon leaves
Kosher salt, freshly ground pepper
3 cups heavy cream
1 cup low-sodium chicken broth
1 1/2 pounds celery root, peeled, sliced 1/16" thick
1 pound rutabaga, peeled, sliced 1/16" thick
1 pound turnips, peeled, sliced 1/16" thick
1 pound Yukon Gold potatoes, peeled, sliced 1/16" thick
2 garlic cloves, thinly sliced

Instructions

Preheat oven to 400 °F. Butter a shallow 2-quart baking dish. Melt 2 tablespoons butter in a medium skillet over medium-high heat. Add breadcrumbs; cook, stirring often, until golden brown, 5 —7 minutes. Transfer to a small bowl and toss with 1/2 cup Parmesan and 1 tablespoon thyme leaves; season with salt and pepper.
Bring cream, broth, thyme sprigs, and remaining 2 tablespoons butter to a simmer in a medium saucepan over medium heat; season with salt and pepper. Remove from heat, cover, and let sit 10 minutes; discard thyme. Cover and keep warm.
Toss vegetables and garlic in a large bowl; season with salt and pepper. Arrange 1/3 of vegetables in dish and top with 1/2 cup Parmesan. Repeat layers; top with remaining vegetables. Pour cream mixture over; place a piece of parchment paper directly on top of vegetables.
Bake until vegetables are crisp-tender and cream is thickened, 50 –60 minutes. Uncover, top with breadcrumbs, and bake until gratin is bubbling and breadcrumbs are brown, 15 –20 minutes longer. Let sit 10 minutes before serving.