Place chicken in a food processor; pulse until coarsely ground.
Heat large nonstick skillet over medium. Add chicken, broth and ginger to pan; cook 8 minutes or until chicken is done, stirring frequently. Drain well and transfer to a large bowl.
Add water chestnuts, red onion, green onions, cilantro, juice, sugar, fish sauce and salt to bowl; toss well.
Place 1/3 c. chicken mixture into each lettuce leaf. Serve with peanuts and serrano.
