Melt butter and saute onion in top of double boiler.
Add clams, cheese and seasoning; cook over hot water until cheese melts.
Serve with melba toast rounds and crackers.(I prefer Vera-Sharp Cream Cheese which comes in a jar.I often use the whole big jar of cheese, which is more than the recipe calls for)
Good in a chafing dish.
Serves 8 or more.