Preparation:  Flake crab meat into strands, removing any cartilage. Mix with sherry.  Wash onions; remove roots and greens; finely mince white part. Wash and pat dry lettuce leaves; arrange on round serving plate. In a mixing bowl, beat egg whites.  When eggs begin to stiffen, slowly add milk. When eggs are stiff, fold in crab, onions, salt and cornstarch. Eggs will tend to break down at this point into a frothy
soup.
  
Stir-frying:  Heat wok to medium hot.  Add oil.  When oil is heated, add egg mixture, carefully folding and turning while eggs become firm. Remove to serving platter. Serve.