I took the best aspects from three different recipes (and added a few tweaks) to make a lettuce wrap that is super flavorful, healthy, less-drippy, and easier to make (no prying the tight leaves off of iceburg lettuce)! I hope you will give this one a try.
1) In a small saucepan combine the soy sauce, sugar, white vinegar, vegetable oil, peanut butter, sesame seeds, and ground ginger. Bring to a boil over medium heat. Stir together the cornstarch and water and add to the pan along with the lemon juice and sesame oil. Stir until sauce thickens, about 3 minutes, then remove from heat.
2) (This cooks up quick so make sure everything is cut & ready to go!) Warm up a large pot (4qt) over medium heat. When hot, add ground chicken, mushrooms, and garlic. Cook for about 5 minutes, stirring frequently & breaking up the chicken into small pieces until cooked through. Spoon out all liquid from the pan.
3) Add the coleslaw mix, water chestnuts, and green onions. Cook for about 2 minutes to wilt the cabbage then stir in the sauce and heat until there is no liquid on the bottom of the pan.
4) Cut the end off of the Romain lettuce to separate the leaves. Cut the tallest outside leaves in half to make them easier to handle and discard the smallest inside leaves. (You may also want to trim the width of the large leaves down to about 6 inches.) To eat, spoon some of the chicken mixture down the center of the leaf and fold in half like a taco.