In a wok or deep-sided frying pan, heat 2 Tbsp. of oil over high heat. Toss chicken with cornstarch and add to the wok or pan. Stir-fry until lightly browned and just cooked, and remove. Heat the remaining oil in wok or pan, add garlic and ginger and cook till fragrant, about 30 seconds. Add the onion and pepper and stir-fry 2 min. more. Add snow peas and stir-fry a few seconds more. Add reserved chicken, sugar, stock, chili sauce, soy sauce and sesame oil. Bring to a simmer and stir-fry about 2 to 3 min. Toss in remaining ingredients, except lettuce, and spoon onto a serving platter. Place on your dinner table with the lettuce nearby. To make the wrap, simply spoon some of the mixture into the middle of a lettuce leaf and fold and roll it around the filling. Steamed rice could also be served alongside.