Preheat oven to 350°F. Drain the clams, reserving the clam juice in a separate dish.
Combine drained clams and all other ingredients except butter. Gradually add reserved clam juice until the mixture has a texture like cookie dough. Scoop mixture into clam shells. (Our family saves the clam shells from one year to the next, storing them in a large plastic storage bag.)
Place 1 small pat of butter (about the size of a quarter) on each filled clam shell and bake 10 to 12 minutes. Makes about 30 small filled shells or 15 to 20 large filled shells.