1.Place sour cream, mayonnaise, juice and rind in a medium bowl. Coarsely grate onion over a small bowl. Press down on onion to extract as much juice as possible; discard onion, reserve onion juice. Add onion juice to sour cream mixture, stir to combine; season.
2.Remove outer leaves from lettuce; discard root end. Cut each lettuce into quarters lengthways (push a 20cm (8-inch) bamboo skewer through the leaves to help to hold the leaves together, if necessary).
3.Arrange lettuce on a large platter. Drizzle with sour cream dressing; sprinkle with shallots and parsley.
Fried asian shallots are found in cellophane bags or jars at all Asian grocery stores; once opened, they will keep for months if stored tightly sealed.Note