Recipe from: What's Cooking America by Linda Stradley and Andra Cook

Ingredients
15 medium (5 pounds) potatoes, peeled and quartered
6 ounces cream cheese, room temperature
1 cup sour cream
2 teaspoons onion powder
1 teaspoon salt
1/2 teaspoon pepper
2 egg whites, slightly beaten
1 tablespoon butter or margarine

Instructions
Spray a large casserole dish with vegetable-oil cooking spray. In a large pot of boiling water over medium-high heat, cook potatoes until tender when pierced with a fork; remove from heat and drain. Mash potatoes until there are no lumps. Add cream cheese, sour cream, onion powder, salt, pepper, and egg whites; blend well. Dot with butter or margarine. Cool slightly, cover, and refrigerate.

Preheat oven to 350 degrees F. Take potatoes out of the refrigerator 30 minutes before baking. Bake, covered, 40 minutes or until steaming hot in center. Remove from oven and serve immediately.

NOTE: This can be made up to a week ahead. If preparing ahead, place in an ovenproof baking dish, allow to cool sllightly, cover, and refrigerate.