Rinse the pork, place on a cutting board, pat dry with paper towels and rub in the salt and pepper. Set the pork in the bottom of a slow cooker, scatter the onion over the pork, sprinkle on the garlic and add the wine. Cook until the pork easily pulls apart with a fork, about 5 hours on high or 8 hours on low. Turn off the slow cooker and transfer the pork to a bowl. Use two forks to shred the pork.

If you don't have a slow cooker, you can braise the pork shoulder in a 325 degrees F oven for 2 1/2 to 3 1/2 hours.