Chicken Lettuce Wraps

Name: Chicken Lettuce Wraps
Ingredients: Dipping Sauce; 1/4 cup low sodium soy sauce; 2 teaspoons rice vinegar; 1 1/2 tablespoons toasted sesame oil; 1 1/2 tablespoons sugar; 3 tablespoons Worcestershire sauce; 1 teaspoon crushed red pepper flakes; 1 1/2 tablespoons garlic, minced; 1 tablespoon ginger, minced; Lettuce Wraps; 2 tablespoons rice vinegar; 1 tablespoon sesame oil; 1 tablespoon Chinese hot mustard, plus more for sautéing; 3 tablespoons light brown sugar; canola oil for frying, plus more for sautéing; 2 ounces Maifun rice sticks (the thin kind), pulled apart; 1 pound ground chicken; Kosher salt; freshly ground black pepper; 1 large clove minced; 3 scallions, thinly sliced; 1 cup water chestnuts, diced; 8 Shiitake mushroom caps, diced; 1 head iceberg lettuce