Peel and quarter potatoes. You will have 7-8 cups peeled potatoes. Put potatoes in large saucepan with water to cover. Bring to a boil and boil until tender, about 20-25 minutes. Drain well. Mash until smooth with potato masher or electric mixer. Mix cream cheese with sour cream or yogurt, onion salt and pepper. Beat into the potatoes and beat with a whisk until smooth and fluffy. Taste for seasoning: you may wish to add a teaspoon of plain salt. Place in two-quart casserole or a refrigerator container. Cool and cover. To serve, place desired amount in greased casserole, dot with butter or margarine and sprinkle with paprika or top with lots of cheese (freshly grated, if possible). Bake at 350 degrees for 30-45 minutes, uncovered, until heated through. Makes 8-10 servings. Tastes best if refrigerated 12-24 hours before baking. Can be kept in covered refrigerator container for up to two weeks. POTATOES WITH CHIVES: Instead of 2 tsp. onion salt, use 1 tsp garlic salt or onion salt, 1 tsp. plain salt, and one tbsp. minced freeze-dried or fresh chives.