1. Cut roast in half. Combine burrito seasoning and cocoa; rub over meat. Place peppers and onion in a 3- or 4-qt. slow cooker; top with meat. Combine broth and ketchup; pour over meat.
2. Cover and cook on low for 8-10 hours or until meat is tender.
3. Skim fat. When cool enough to handle, shred meat with two forks and return to slow cooker; heat through. Using a slotted spoon, spoon 1/2 cup onto each bun. Yield: 8 servings.