Season the beef with black pepper and coat with flour. Heat the oil in a skillet. Add the beef and cook until browned.
Place the onions, potatoes, carrots, garlic and thyme in a 3 1/2-quart slow cooker. Top with the beef. Mix the tomato paste, coffee and 1 cup broth. Pour the coffee mixture and the remaining broth into the slow cooker. Cover and cook on LOW 8 to 10 hours.* or until done. Serve with the sour cream and chopped green onions, if desired.