Before cooking, make sure you have everything available on hand, prepped, and ready to cook. These lettuce wraps go together super quickly.
In a small bowl, mix together the dark soy sauce, wine, sugar, and oyster sauce, set aside.
Place a large skillet or wok over medium-high heat. Once hot, add the oil and swirl it around the pan to coat. Add the chicken, mushrooms, water chestnuts, and white part of the green onions to the pan. Season with a pinch of salt and pepper. Break up the chicken into small crumbles, tossing everything to combine. Lightly brown the chicken, stirring occasionally, until fully cooked through. About 8 minutes total time.
Pour the sauce into the pan and stir to combine everything in the sauce. Keep cooking for about another 2 minutes just to ensure everything is well coated in the sauce and any excess has time to evaporate.
Stir in half of the green part of the onion.
Take off the heat and serve with the lettuce cups and the remaining green part of onions to top each wrap. You can serve the head of lettuce right on the table so everyone can rip off a lettuce cup to serve themselves or, you can separate the lettuce leaves and place them on a plate before serving.