Wash hands with soap and water.
Gently rub green onions and lettuce leaves under cold running water. Slice green onions.
Combine sauce ingredients in small bowl. Set aside.
Brown ground beef in large nonstick skillet over medium heat until internal temperature reaches 160 °F on food thermometer. Break beef up into small crumbles. Pour off drippings, if necessary.
Add green onions and soy sauce; season with pepper, as desired. Cook and stir for 1 minute.
Evenly spoon beef mixture onto each lettuce leaf. Top with equal amounts of water chestnuts and carrots. Spoon some sauce over top.
Wash hands with soap and water.
Wrap lettuce around filling. Serve with remaining sauce.