Potato Soup

1 Tbsp. Chopped Onion 2 Tbsp. Butter 1 Tsp. Salt 1/4 Tsp. Celery Salt 1/8. Tsp. Pepper 1 Cup Mashed Potatoes 2 Cups Hot Milk Saute onion in butter. Add seasonings and potatoes. Stir in milk. Simmer slowly for about 5 minutes, stirring occasionally. 6...