Step 1: Prepare the Lettuce : Separate the lettuce leaves carefully, rinse them under cold water, and pat them dry with paper towels. Keep them in the fridge until ready to serve for extra crispness.
Step 2: Mix the Sauce : In a small bowl, whisk together hoisin sauce, soy sauce, rice vinegar, oyster sauce, sriracha, and brown sugar. Set aside — this mixture will give the chicken its deliciously sticky, savory flavor.
Step 3: Cook the Chicken : Heat sesame oil and vegetable oil in a large skillet or wok over medium-high heat. Add garlic, ginger, and onion; sauté for 2–3 minutes until fragrant. Add ground chicken and cook for 5–6 minutes, breaking it apart until no longer pink.
Step 4: Add Vegetables : Stir in diced bell pepper, mushrooms, and water chestnuts. Cook for 3–4 minutes until vegetables are softened and any moisture has evaporated.
Step 5: Add the Sauce : Pour the prepared sauce mixture into the skillet. Stir well to coat everything evenly, and simmer for 2–3 minutes until the sauce thickens slightly. Toss in chopped green onions for freshness.
Step 6: Assemble the Wraps : Spoon the warm chicken mixture into chilled lettuce leaves. Garnish with extra green onions, crushed peanuts, or sesame seeds.