Place chicken breasts in slow cooker, and pour salsa over the top. Set the slow cooker to low and let cook for 8 hours.
Pull the chicken breasts out of the slow cooker, and using two forks, shred the meat. Add the shredded chicken breast back into the juices in the slow-cooker, and stir around. Then pull the meat back out and toss the juices.
Warm black beans up on the stove and top with cheese and cilantro. If you like, warm the tortillas up for a minute to make them pliable.
Next, fill your tacos. We used the shredded chicken, Greek yogurt (in place of sour cream), cheese, lettuce, and tomatoes. Serve with black beans!