Mashed Potato Gratin from Cooking Light

I love, love, LOVE this recipe. It is perfect for a pot luck or a fancy Thanksgiving feast. 

Although Yukon Gold potatoes give this cheesy gratin extra buttery flavor and color, russets will also work.

ingredients
4 pounds Yukon gold potatoes, peeled and cut into 2-inch chunks
1 cup (4 ounces) fontina cheese, shredded and divided
3/4 cup (3 ounces) Gruyere cheese, shredded and divided
1 1/2 tablespoons butter
1 teaspoon salt
1/4 teaspoon freshly ground black pepper
1 cup warm 1% low fat milk (100 - 110 degrees)
Cooking spray

1. Preheat oven to 400 degrees.
2. Place potatoes in a large Dutch oven. Cover with water; bring to a boil. Reduce heat, and simmer 15 minutes or until tender; drain. Return potatoes to pan. Add 3/4 cup fontina cheese, 1/2 cup Gruyere cheese, butter, salt and freshly ground black pepper to pan; mash with a fork or potato masher until well combined. Add warm milk to pan; continue mashing potato mixture until desired consistency. Spoon into a 13x9-inch  baking dish coated with cooking spray; sprinkle evenly with remaining 1/4 cup fontina cheese and remaining 1/4 cup Gruyere cheese. Cover with aluminum foil lightly sprayed with cooking spray. Bake at 400 degrees for 20 minutes. Remove from oven; remove and discard foil. 
3. Preheat broiler.
4. Broil gratin 5 minutes or until cheese is brown and bubbly. 

Yield: 14 servings. (Serving size: 1/2 cup)