Pre-heat oven to 350 degrees F. Place ground pork in the disposable aluminum pan, breaking it up and spreading evenly. Bake until browned and cooked through, stirring several times to break it up, about 50 - 60 minutes. When done, remove the pork from the oven, break up into small 1/2 size pieces and set aside.
Meanwhile, in 1 - 2 large skillets over medium heat, add the sesame oil, onions and mushrooms. Sauté until mushrooms are tender and golden brown and the onions are translucent and soft, stirring frequently.
To the mushroom and onion mixture, add the garlic, reduce heat to medium and cook 30 seconds or until fragrant, stirring frequently. Add the garlic, soy sauce, hoisin sauce, ginger, rice wine vinegar, water chestnuts and shredded cabbage to the pan, stir, and let simmer 2 minutes. Remove from heat and set aside.
Add the mushroom and onion mixture to the disposable pan containing the pork. Mix well to thoroughly combine.
To serve, pile the lettuce leaves on a plate. Serve the hot pork mixture from the pans, sprinkling with white sesame seeds and 1 bunch green onions cut on the diagonal. Serve the dipping sauce in several bowls with spoons to allow people to spoon over the chicken mixture.
Slow Cooker Instructions: Can be kept warm on LOW for 2 hours until ready to serve. If mixture becomes too dry, rehydrate with a splash of chicken broth or water.