Place bread slices in a shallow dish; cover with water. Let stand 1 minute or until bread soaks up water; squeeze excess water from bread.
Pulse walnuts in a food processor just until finely ground. Add bread, garlic, and sour cream; pulse until blended. With processor running, slowly add vinegar and oil through food chute. Combine walnut mixture, salt, pepper, and lobster in a large bowl.
Place 1/2 cup lobster mixture in the center of each lettuce leaf. Garnish, if desired.
*Cook 3, whole 1-pound lobsters and garnish each plate with claw meat.