Heat the canola oil in a medium saucepan set over medium heat. Add the garlic and cook until fragrant, about 30 seconds.
Add the ketchup, cider vinegar, molasses, Dijon mustard, Worcestershire sauce, chipotle pepper and adobo sauce. Whisk to combine. Heat the sauce until simmering.
The Chicken:
Season the chicken thighs with salt and pepper.
Heat the oil in a large skillet set over medium-high heat. Add half of the chicken and brown on both sides, 2 to 3 minutes per side. Repeat with the remaining chicken.
Place the chicken into the bottom of a large slow cooker.
Pour the barbecue sauce over the chicken and turn to coat.
Set the slow cooker to LOW and cook until the chicken is tender, about 4 hours.
Transfer the chicken to a cutting board and shred with 2 forks. Return the chicken to the slow cooker and toss to coat with the sauce.
The Slaw:
In a medium bowl, whisk together the Kefir, cider vinegar, honey, Dijon mustard, salt and pepper.
In a large bowl, toss together the green and purple cabbage, shredded carrot and cilantro. Toss to coat with the dressing.
Pour the dressing over the slaw mixture and toss to coat.
Putting it Together:
Place one hamburger bun half on each of 8 plates. Top each with ½ cup of the chicken mixture and ½ cup of the slaw. Serve.