In a medium bowl, combine the bamboo shoots, water chestnuts, sherry, hoisin sauce, peanut butter, soy sauce, hot-pepper sauce, and sugar substitute. Mix well and set off to the side.
Mist a large, non-stick skillet with olive oil spray and place over medium heat. Add the garlic and cook for 2 minutes, or until fragrant. Add the onion and cook, stirring periodically, for 3 to 4 minutes or until tender and just beginning to brown.
Increase the heat to medium-high. Add the chicken, ginger, and salt. Cook, splitting the chicken into small pieces, for 3 to 4 minutes, or until no longer pink.
Add the reserved bamboo shoot mixture. Cook for 2 minutes, or until hot. Stir in the sesame oil.
Remove the pan from heat and spoon the chicken mixture, in equal amounts, into the lettuce leaves. Set on a serving dish, topping with onion and cucumber. Serve immediately.