Directions

• Place russet potatoes in a Dutch oven and cover with water. Bring to a boil. Reduce heat; cover and cook until tender, 10-15 minutes.
• Meanwhile, place sweet potatoes in a large saucepan; cover with water. Bring to a boil. Reduce heat; cover and cook until tender, 10-15 minutes. Drain; mash with half of the cream cheese and sour cream and all of Colby cheese.
• Drain russet potatoes; mash with the remaining cream cheese and sour cream. Stir in the milk, Parmesan cheese, salt and pepper.
• Spread 2-2/3 cups russet potato mixture into each of 2 greased 11x7-in. baking dishes. Layer with 4 cups sweet potato mixture. Repeat layers. Spread with remaining russet potato mixture.
• Bake, uncovered, at 350° until heated through, about 15 minutes. Combine topping ingredients; sprinkle over casseroles. Bake until cheese is melted, 2-3 minutes longer.