In a small mason jar or bowl, combine the sauce ingredients. Whisk well with fork and set aside.
In a large pan over medium-high heat, add the ground pork, diced mushrooms, diced onion and a little salt and pepper. Cook for about 4-5 minutes stirring occasionally. Add water chestnuts and continue to cook until pork is cooked through.
Turn the heat down to medium-low and add the sauce to the pan plus 2 tablespoons additional water (add the water to the empty mason jar that contained the sauce, then shake up and pour in).
Bring to a low simmer and continue to cook for 5-7 minutes or until sauce is mostly absorbed. Stir occasionally.
Serve pork in lettuce leaves with desired toppings.
