Mix the tomato paste and coffee in a small bowl; set aside. Toss the meat with the chili powder, 1 1/2 teaspoons salt and 1/4 teaspoon pepper in a 6-quart slow cooker. Stir in the beans (with their liquid), the coffee mixture and the tortilla chips.
Cover the slow cooker and cook on low until the beef is tender, 8 hours. Season with salt. Serve the chili with the rice; top with cheese, scallions and avocado.