Cook potatoes in large pot of boiling water until tender, about 20 minutes. Drain; mash until there are no lumps. Add cream cheese, sour cream, onion powder, salt, pepper and egg whites; blend well. Spray a 9-by-13-inch casserole with nonstick cooking spray. Add potato mixture. Dot with butter. Cool slightly, cover and refrigerate up to 7 days. Take out of refrigerator 30 minutes before baking. Preheat oven to 350 degrees. Bake, covered, 40 minutes or until steaming hot in center.
Note: Alternatively, potatoes can be reheated in a slow-cooker. Take potatoes out of refrigerator about 3 1/2 hours before you plan to serve them. Place in slow-cooker. Dot with butter. Cook on low heat for 3 hours, stirring once or twice. They can be held an additional 30 minutes or longer.
PER SERVING: calories: 224 (27% from fat); protein: 6 grams; total fat: 7 grams; saturated fat: 4 grams cholesterol: 21 mg; sodium: 287 mg; carbohydrate: 35 grams; dietary fiber: 3 grams
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