Directions
1. Place the pork shoulder in a slow cooker. Top with onions and barbecue sauce. Cook on the lowest heat setting for 8-10 hours (or on high for 4-5 hours).
2. Remove pork from slow cooker. Discard any excess fat. Using two forks, shred the pork. Return to the slow cooker and stir until evenly coated with sauce.
3. Assemble the nachos. On a large platter, spread half the tortilla chips and cover with a layer of pork. Sprinkle with cheese. Repeat with another layer of chips, pork and cheese. Top with sour cream and cilantro leaves. Serve with guacamole.