Start by cubing and seasoning your meat. This will make it easier to cook as and add a lot of flavors because more meat surfaces will come in contact with the marinating sauce. At this time, also put your dried chiles into a bowl with hot water to rehydrate them
Brown the beef. This is a crucial step. This step is what makes or breaks a meat dish. It is not the same to slow cook a piece of raw meat as slow cook a piece of browned meat. The flavors that develop when browning the meat really make a huge difference in the final taste of the dish. Do not skip this step.Transfer the brown cubes of meat to the slow cooker.
Make the marinating sauce: into a blender pour the beef broth and add the garlic, rehydrated chiles, chipotles in adobo, vinegar, lime juice, and spices.
Blend everything very well to make a thick sauce. This will be both the marinade and the cooking liquid for the meat. If you feel it needs more liquid, add 2 extra tablespoons of broth, but you don’t want it to be too liquid. It has to be a bit thick, or else your meat will have way too much liquid.
Add the chopped onion, sauce and bay leaves to the crockpot on top of the meat, stir it, and cook on high for 4-5 hrs or on low for 8 hrs until the meat is tender enough to be shredded with the use of two forks.
After shredding the beef, return it to the crockpot and mix it with the remaining marinade and rendered juices. The meat should be moist but not have excess liquid.
Serve with corn tortillas and the toppings of your choice.