In a saucepan melt butter and add onions and garlic and saute until translucent. Add remaining ingredients and bring to a boil, then simmer for 45 minutes. Braise pork in this sauce for 2 1/2 to 3 hours until fork tender enough to pull with fork. Strain liquid and reserve. When the pork is cooled, pull or shred the meat with fork or fingers. Reheat the pork in the reserved sauce. Serve as a sandwich with coleslaw and sesame seed buns.