Place chicken in a 2-quart pan with the onion, ginger, sherry, salt, sugar and water. Bring to a boil, cover and simmer for 20 minutes. Remove from heat and let stand until chicken is cool enough to handle. Strain broth and save for soup. Remove and discard skin from chicken. Pull meat from bones, then pull meat in long shreds. If made ahead, cover and chill. Sauce Stir together peanut butter and salad oil until blended. Stir in soy sauce, sugar, vinegar, sesame oil, red pepper, green onion and cilantro. To serve, mound lettuce on a serving platter. Arrange shredded chicken over lettuce. Drizzle peanut sauce over all.