1Add avocados and onion in blender. Season lightly with salt and Worcestershire sauce. Add tomato juice and blend to a paste. Once blender is turned on, if paste does not blend smoothly, add a small amount of tomato juice until it flows smoothly.
2Pour ingredients from blender into the center of a salad bowl. Stand lettuce leaves (which have been washed and separated) around the edge of the bowl, working from the outer perimeter to the center, as if you were shaping a flower.
3As an appetizer, the guests serve themselves with their fingers, using the lettuce to dip into the paste.