In a large frying pan on medium heat, sautee the chicken until no longer pink inside, breaking it up as it cooks. Once cooked, add into the bottom of a 7 quart slow cooker.
Place the cauliflower into a food processor and process until broken down and "rice like." Add the cauliflower rice, along with all the other ingredients up to the water chestnuts (including them) into the slow cooker and stir to combine.
Place all the other ingredients in a medium, microwave-safe bowl and microwave for 10-20 seconds, until the peanut butter is smooth. Whisk until smooth and creamy.
Pour the sauce over the ingredients in the slow cooker and stir to combine. Cover and cook on low until the vegetables are tender, about 1.5-2 hours, depending on your slow cooker.
Serve in lettuce and garnish with peanuts, cilantro and green onion!