A mandoline will slice the veggies into uniform thickness and make quick work of it. Use a flavorful aged Gruyère cheese, if you can find it. If not, substitute an equally assertive cheese, such as aged cheddar, Gouda, or a pungent soft-ripened cheese, like Brie.
3 3/4 cups (1/8-inch-thick) slices peeled turnip
3 3/4 cups (1/8-inch-thick) slices peeled parsnip
6 cups water
1 cup whole milk
1/3 cup fat-free, less-sodium chicken broth
2 tablespoons all-purpose flour
1 teaspoon kosher salt
1/2 teaspoon freshly ground black pepper
1 cup (4 ounces) shredded Gruyère cheese
2 tablespoons butter
1/4 cup panko (Japanese breadcrumbs)
How to Make It
Preheat oven to 400°.
Combine first 3 ingredients in a large saucepan; bring to a boil. Reduce heat, and simmer 7 minutes or until almost tender. Drain; let stand 5 minutes. Arrange about 1/2 cup vegetable mixture into each of 8 (5 1/2-inch) round gratin dishes coated with cooking spray.
Combine milk, broth, flour, salt, and pepper in a saucepan over medium-high heat; bring to a simmer. Cook 4 minutes, stirring constantly with a whisk until thick. Remove from heat; add cheese, stirring with a whisk until smooth. Spoon about 3 tablespoons sauce over each serving.
Melt butter in a medium skillet over medium-high heat. Add panko; toast 2 minutes, stirring constantly. Sprinkle breadcrumb mixture evenly over cheese mixture. Place dishes on a baking sheet. Bake at 400° for 15 minutes or until bubbly and golden brown on top. Let stand 5 minutes before serving.