Combine the lime juice, fish sauce, vinegar, sugar and pepper in a large bowl. Stir to dissolve the sugar. Add the thinly sliced onions and push them down so that they are covered by the dressing. Let soak for 25-30 minutes (you may also just pile the rest of the ingredients on the top and store in the refrigerator and toss when ready to serve).
Add the cabbage, carrots, mint, and chicken to the bowl and toss to coat everything. Serve on plates and top with the peanuts.
Serve at room temperature or chilled.
Notes
Lime Juice - use fresh squeezed. If you like a little heat, use a sliced chili pepper in the dressing.Cabbage - use green, purple or napa.