Use the slicing blade of a food processor for uniform slices. Substitute fontina or Monterey Jack if you are not a blue cheese fan.
- 2 tablespoons butter
- 2 1/2 tablespoons all-purpose flour
- 1 teaspoon chopped fresh thyme
- 2 1/2 cups fat-free milk
- 3/4 cup (3 ounces) crumbled Gorgonzola or other blue cheese
- 1 1/2 teaspoons salt
- 1/4 teaspoon freshly ground black pepper
- 3 pounds baking potatoes, peeled (and cut into 1/8-inch-thick slices)
- cooking spray
- 1/3 cup (1 1/2 ounces) grated Parmigiano-Reggiano cheese
Preheat oven to 375°. Melt butter in a small saucepan over medium-high heat. Add flour, and cook 2 minutes, stirring constantly with a whisk. Stir in the thyme. Gradually add milk, stirring with a whisk; cook over medium heat until slightly thick (about 3 minutes), stirring constantly. Stir in the Gorgonzola; cook 3 minutes or until cheese melts, stirring constantly. Stir in salt and pepper. Remove from heat.
Arrange one-fourth of potatoes in bottom of a 13 x 9-inch baking dish coated with cooking spray; spoon about 3/4 cup sauce over potatoes. Repeat layers twice; arrange remaining potatoes over sauce. Sprinkle with Parmigiano-Reggiano. Cover and bake at 375° for 30 minutes. Uncover and bake an additional 40 minutes or until potatoes are tender. Remove from oven; let stand 10 minutes before serving.