1. Make the special sauce (for spooning over your lettuce wraps) by dissolving the 1/4 cup sugar in 1/2 cup water in a small bowl.
2. Add 2 tablespoons soy sauce, 2 tablespoons rice vinegar, 2 tablespoons ketchup, 1 tablespoon lemon juice and 1/8 teaspoon sesame oil.
3. Mix well and refrigerate this sauce until you're ready to serve the lettuce wraps.
4. Combine the 2 teaspoons water with the Chinese hot mustard and set this aside as well.
5. Eventually you will add your desired measurement of Chinese mustard and garlic chili sauce to the special sauce mixture to pour over your lettuce wraps.
6. In the restaurant chain, skilled master craftsmen prepare the sauce at your table the same way, depending on your desired heat level.
7. To prepare the filling for your lettuce wraps, bring 2 tablespoons of vegetable oil to high heat in a wok or large frying pan.
8. Sauté the chicken breasts for 4 to 5 minutes per side or until done.
9. Remove chicken from the pan to cool.
10. Keep the oil in the pan and keep the pan hot.
11. As the chicken cools be sure your water chestnuts and mushrooms have been minced to about the size of small peas.
12. Prepare the stir fry sauce by mixing the soy sauce, brown sugar, and rice vinegar together in a small bowl.
13. When you can handle the chicken, hack it up with a sharp knife so that no piece is bigger than a dime.
14. With the wok or pan still on high heat, add an additional tablespoon of vegetable oil.
15. Add the chicken, garlic, water chestnuts, onions, and black mushrooms to the pan.
16. Add the stir fry sauce to the pan and sauté the mixture for a couple minutes then serve it onto into a dish lined with a bed of fried rice noodles (maifun).
17. Serve chicken with a side of lettuce cups.
18. Make these lettuce cups by slicing the top off of a head of iceberg lettuce right through the middle of the head.
19. Pull your lettuce cups off of the outside of this slice.
20. Make the special sauce at the table by adding your desired number of mustard and chili sauce to the special sauce blend: 1 teaspoon mustard and chili sauce for mild, 2 teaspoons each for medium and 3 teaspoons of each for hot.
21. Stir well.
22. Assemble lettuce wraps by spooning filling into a lettuce cup, adding special sauce over the top, folding it up like a taco.
23. *Tidbits:Follow the directions on the package for frying the maifun (rice sticks)-- usually by pouring 2 inches of vegetable oil into a pan and heating to around 400 degrees.
24. Add maifun, a little at a time, and when it floats to the top remove it to a paper towel.