Start by making the bread and milk paste (panade). Place the bread and milk into a large bowl. Then, using a fork, mash together until paste forms.
Add the ground beef, salt, and pepper into the paste, then use your hands to mix. Place the ground beef into the crockpot.
In a medium bowl, stir the onions, garlic, chili powder, cumin, coriander, and oregano with olive oil. Microwave for 4 – 5 minutes. This step blooms the spices, which adds more flavor to the aromatics. Add the onion mixture in with the beef.
Stir the tomato sauce, cider vinegar, and brown sugar together, and then add into the slow cooker with ground beef and the onion and spice mixer.
Slowly mix, breaking up large chunks of ground beef. You’ll break the meat up more after it cooks. In this step, you just want to mix the ingredients.
Set the crockpot to cook on low for 6 - 8 hours or high for 3 hours.
After the ground beef cooks use a spoon to break it into smaller pieces. If you’re using it, stir in the black beans.
Serve with taco shells or use in your favorite Mexican-inspired recipe that calls for taco meat.