Place onions on bottom of slow cooker. Place pork on top. Sprinkle with apples. In a large bowl, mix chill sauce, mustard, honey, chill powder, tomato paste, worcestershire sauce, sugar, paprika, and garlic. Pour over meat and cook on low for 6 to 7 hours. Remove roast to large plate. Using 2 forks shred meat in opposite directions. Serve on buns.