In a medium bowl, using a fork, mash together the milk and bread until it forms into a paste. Using your hands mix in the ground beef, salt, and pepper. Set aside ** the bread and milk paste help to keep the beef moist throughout the slow cooking process.
In another medium bowl stir together the vegetable oil, onions, garlic, chili powder, cumin, coriander, and oregano. Microwave for 4 – 5 minutes. This blooms the spices which keeps the flavors pronounced during the slow cooking process.
Add the onion and spice mixture along with the beef mixture into the slow cooker. Next stir in the tomato sauce and cider vinegar. Without over mixing break up some of the larger pieces of beef.
Cook on low 6 to 8 hours.
When done use a spoon to break up the beef into smaller pieces or whatever texture you prefer. If using, stir black beans inches.