Mix shoyu, lemon juice, vinegar, sugar, and peppercorns in a microwave-safe bowl. Heat for one minute; set aside.
Bring the water, ginger, and onion to a boil in a medium saucepan over medium heat. Lower heat to a simmer and add chicken. Cook for 15 minutes. Turn off heat and let chicken sit in liquid for 10 minutes. Remove chicken from stock, cool, then shred. Place chicken in a bowl, add a little stock to keep moist, then refrigerate until ready to use.
Place a chunk of cucumber under the broad part of a kitchen knife. Lightly crush cucumber by carefully hitting the blade with your fist. Repeat with remaining pieces. Place lettuce on a serving platter. Arrange a layer of cucumbers around lettuce. ;Remove the cold chicken from the stock and place it down in the center of the platter. Surround the chicken with tomato wedges and top it with green onions and optional Chinese parsley.
In a small pan, heat sesame oil over medium heat until bubbles appear. Turn off heat and pour oil evenly over green onions, Chinese parsley and chicken; set aside. In small bowl combine vinaigrette ingredients, strain and drizzle it over the salad. Add salt and pepper to taste. Makes 6 servings.
Approximate Nutrient Analysis per serving (not including salt to taste):
230 calories, 12 g fat, 2 g saturated fat, 55 mg cholesterol, 500 mg sodium, 11 g carbohydrate, 3 g fiber, 6 g sugar, 21 g protein