Beat butter at high speed with an electric mixer until fluffy. Add cracker crumbs, egg yolk, and garlic, beating until blended. Stir in parsley and next 5 ingredients. Place butter mixture on wax paper, and roll into a log 1 1/2-inches in diameter. Chill until firm.
Open clams, and discard top shell. Loosen meat from bottom shell, and rinse in cold water.
Cut butter into 1/8-inch-thick slices, and place 1 slice on each clam.
Broil 5 inches from heat 5 minutes or until golden brown.
NOTE: Any remaining butter can be wrapped and stored in the freezer or refrigerator. Because of the risk of salmonella in the raw yolk, butter must be cooked in a heated recipe and not used as a cold spread.