5 pounds potatoes (about 6 large) 
1/2 cup butter, divided 
1/2 cup chopped fresh mushrooms 
2 tablespoons all-purpose flour 
1 cup 2% milk or half-and-half cream 
1 teaspoon salt 
1/2 teaspoon pepper 
1/2 teaspoon dried thyme 
2 cups shredded sharp cheddar cheese 
2 cups sour cream 
1 medium onion, chopped 
1/2 cup dry bread crumbs 
1/4 cup grated Parmesan cheese
1. Place whole potatoes in a large stockpot; add water to cover. Bring to a boil. Reduce heat; cook, uncovered, until tender, 20 to 25 minutes. Drain. 
2. Meanwhile, in a large saucepan, heat 1/4 cup butter over medium-high heat. Add mushrooms; cook and stir 2 to 4 minutes or until tender. Stir in flour until blended; gradually whisk in milk, salt, pepper and thyme. Bring to a boil, stirring constantly; cook and stir until thickened, 1 to 2 minutes. 
3. Peel and cube potatoes when cool enough to handle. Press through a potato ricer or strainer into a large bowl; stir in cheddar cheese, sour cream, mushroom mixture, onion and remaining butter. Transfer potato mixture to a greased 13x9-in. baking dish. Refrigerate, covered, overnight. 
4. Preheat oven to 375°. Remove potatoes from refrigerator; uncover and let stand while oven heats. Sprinkle with bread crumbs and Parmesan cheese. Bake, uncovered, until heated through, 55 to 65 minutes.
Prize Winning Recipe
TOTAL TIME: Prep: 1 hour + chilling Bake: 55 min. 
YIELD: 16 servings (3/4 cup each). 
Nutrition Facts
3/4 cup: 283 calories, 16g fat (11g saturated fat), 52mg cholesterol, 345mg sodium, 25g carbohydrate (4g sugars, 2g fiber), 8g protein.