In a mixing bowl cream the butter with the onion, garlic, lemon juice, Worcestershire sauce, salt and pepper. Transfer the mixture to a piece of wax paper and roll up into a cylinder about 3/4-to 1-inch in diameter. Twist the paper at both ends to seal. Refrigerate until firm. Grill the sardines over hot charcoal for 5 minutes per side. Slice the butter into 6 rounds and serve 1 round with each portion.
