In a small bowl, whisk together the peanut butter, rice vinegar, sesame oil, soy sauce, sugar, red pepper flakes and water. Pour into a serving dish and set aside.
Prepare lettuce ‘cups’ by removing the core from a head of lettuce then peel leaves, one by one, from the head of lettuce. Rinse lettuce cups in cold water then pat dry. Refrigerate until ready to serve.
Place large skillet over medium-high heat then add the ground chicken and salt. Break chicken into small pieces and cook just until no pink remains—about 5 minutes. The chicken does not need to be cooked through—just give it a head start.
Add onions, mushrooms, garlic and ginger then cook an additional 3–4 minutes, until onion softens and becomes translucent. Dissolve the cornstarch in the water and add the soy sauce, red wine vinegar and red pepper flakes. Pour this mixture over the chicken and stir to combine then allow the liquid to come to a bubble. Reduce heat to medium-low and let chicken cook in the sauce about 5 minutes.
Stir in shredded carrots and sliced green onions and cook just until they are heated and the green onion begins to soften. Remove from heat then stir in sesame oil. Transfer filling to a serving dish and serve with crispy cold lettuce cups filled to the brim with this yummy filling and lightly drizzle with peanut sauce. Enjoy!
Despite the lack of visible wheat in this recipe, make sure you purchase gluten-free soy if you are serving this dish to a gluten-intolerant crowd!