Drain clams and put aside the liquid. Mix the clams, chicken, and cream cheese together. Add enough of the clam liquid to make the mixture smooth. Add onion, mayonnaise, salt, and pepper to the mixture. Be sure to mix well. Put approximately 1 teaspoon full on each melba toast round and sprinkle with a little parsley for color. You could garnish each melba round with a small slice of carrot or olive, however, garnish (other than the parsley) is not included in this recipe's total for nutritional information. If desired, you may update the recipe to include the garnish of choice and thereby include the garnish's nutritional value into the recipe total (and individual serving nutritional data).