Bring a large pot of salted water to boil. Remove and discard core from cabbage. Put cabbage in boiling water, cover, and gently boil for 5-10 minutes until head is softened. Drain well, and set aside to cool.
Finely chop green onions. In a medium skillet over moderate heat, add vegetable oil. Cook chicken or turkey over medium heat until well done. Add onions, stirring for about 3 munutes. Stir in sugar.
Finely chop ginger to measure 2-1/2 Tablespoons. Finely chop water chestnuts. Add ginger and water chestnuts to meat mixture, along with 1-1/2 Tablespoons soy sauce, water, lemon juice, and black pepper to taste. Mix well and cook 1 minute more. Remove from heat and transfer to a bowl. Cool slightly.
To prepare sauce, whisk together rice vinegar, 1/2 Tablespoon soy sauce and sesame seed oil until combined well.
Peel off eight cabbage leaves from cooled head. Place 4 Tablespoons of filling in center of each leaf and drizzle 1 teaspoon sauce over each mound of filling. Fold stem end over filling, then fold in sides and roll up. Serve immediately, using extra sauce for dipping.