Cook potatoes in boiling, lightly salted water for 20 to 25 minutes or till tender; drain.
Mash potatoes. Add cream cheese, egg, 1/4 teaspoon salt, and dash pepper; beat till smooth. Stir in onion and pimiento. If mixture seems dry, stir in 1 to 2 tablespoons milk
Transfer to buttered 1-quart casserole. Bake, covered, in 325 degree oven 40 to 45 minutes. Makes 6 to 8 servings.
Prepare recipe as above, except cover and refrigerate 3 to 24 hours. To serve, bake, covered, in a 325 degree oven for 1 to 1-1/4 hours or till casserole is heated through.