From my Slow Cooker Recipes book, this slow-cooker shredded beef is very similar to Chipotle barbacoa. Beef chuck roast is cooked with a sauce made from guajillo chiles, jalapeños, onion, garlic, oregano, cumin, mustard seed and allspice, with a little vinegar and Worcestershire. Use it in burritos, tacos, potato chip nachos, on super nachos, or on