Potato Gratin with Mustard and Cheddar Cheese

Preparation Melt butter in heavy large skillet over medium heat. Add breadcrumbs and stir until crumbs are golden brown, about 10 minutes. Cool crumbs (Can be prepared 2 days ahead. Cover and let stand at room temperature.) Position rack in center of oven and preheat to 400°F. Butter 15x10x2-inch (4-quart) glass baking dish. Mix thyme, salt and pepper in small bowl. Combine grated cheddar cheese and flour in large bowl; toss to coat cheese. Arrange 1/3 of potatoes over bottom of prepared dish. Sprinkle 1/3 of thyme mixture, then 1/3 of cheese mixture over. Repeat layering of potatoes, thyme mixture and cheese mixture 2 more times. Whisk chicken broth, whipping cream and mustard in medium bowl to blend. Pour broth mixture over potatoes. Bake potatoes 30 minutes. Sprinkle buttered crumbs over. Bake until potatoes are tender and top is golden brown, about 1 hour longer. Let stand 15 minutes before serving.

Preparation Melt butter in heavy large skillet over medium heat. Add breadcrumbs and stir until crumbs are golden brown, about 10 minutes. Cool crumbs (Can be prepared 2 days ahead. Cover and let stand at room temperature.) Position rack in center of oven and preheat to 400°F. Butter 15x10x2-inch (4-quart) glass baking dish. Mix thyme, salt and pepper in small bowl. Combine grated cheddar cheese and flour in large bowl; toss to coat cheese. Arrange 1/3 of potatoes over bottom of prepared dish. Sprinkle 1/3 of thyme mixture, then 1/3 of cheese mixture over. Repeat layering of potatoes, thyme mixture and cheese mixture 2 more times. Whisk chicken broth, whipping cream and mustard in medium bowl to blend. Pour broth mixture over potatoes. Bake potatoes 30 minutes. Sprinkle buttered crumbs over. Bake until potatoes are tender and top is golden brown, about 1 hour longer. Let stand 15 minutes before serving.