Place the cabbage leaves in the bottom of the slow cooker. Place the pork butt on top of the cabbage (fat cap side up) and add the ketchup, chipotle peppers, and adobo sauce. Pour the Cheerwine on top and cook on high for 4-5 hours (or on low for 8 hours). Halfway through the cooking time, flip the pork butt over.
After the initial cooking time is over, very carefully remove the meat and cabbage leaves from the slow cooker and place on a large cutting board or platter. Discard cabbage leaves (or eat them as a snack) and shred the pork using two forks; pulling the meat and the forks away from each other. The meat should be very tender at this point. Place the shredded pork back into the slow cooker and continue to cook for an additional hour. Top onto a roll or bun of choice and serve.