In a small bowl, whisk together all the spice rub ingredients: chili powder, ground cumin, kosher salt, garlic powder, onion powder, smoked paprika, ground pepper, ground coriander, and chipotle chili pepper. Set this mixture aside, as it will be the flavor base for your beef.
Pat the pieces of boneless beef chuck roast dry with paper towels. This step is crucial as it helps the spices stick better. Liberally season all sides of the beef with your spice rub, gently pressing the spices into the meat. Save any excess spice blend to add later in the cooking process for a flavor boost.
In a large cast-iron skillet or Dutch oven, heat vegetable oil over medium-high heat until it’s sizzling. Once hot, carefully add the seasoned beef pieces. Allow them to sear on all sides, which should take about 4 to 5 minutes. Look for a nice golden-brown crust to develop; this is where the flavor comes from!
Once the beef is seared, transfer it to a 6-quart (or larger) slow cooker. Add all remaining ingredients, including reduced sodium beef broth, mild salsa, diced green chilies, tomato paste, lime juice, brown sugar, and any reserved spices. Stir everything together to combine well.
Cover the slow cooker and set it to cook. Choose HIGH for about 3.5 to 4.5 hours or LOW for 6 to 8 hours. The goal is to cook until the beef shreds easily with two forks. Don’t rush this step; the longer it cooks, the better the flavor!
When the cooking time is up, carefully remove the beef from the slow cooker to a rimmed plate or large bowl. Avoid discarding the delicious juices left in the slow cooker. Shred the beef with two forks, discarding any excess fat.
Return the shredded beef back into the slow cooker, tossing it with the juices. Let it cook on LOW for another 20 minutes. This step allows the beef to soak up all that incredible flavor.
Before serving, taste the shredded beef and adjust the seasoning if necessary. This is the perfect time to add a splash of hot sauce, a sprinkle of cayenne pepper, or a little more lime juice and brown sugar to suit your taste.
To serve, use a pair of tongs to remove the beef from the slow cooker and place it in a serving bowl. I recommend straining out the liquid if you're using it for tacos or burritos to avoid sogginess. Save that liquid to cook rice or another side dish; it’s packed with flavor!
Enjoy your Mexican Shredded Beef in tacos, burritos, quesadillas, salads, or even on nachos. The possibilities are endless, and it’s sure to become a family favorite!