As beef tongue is one of the forgotten cuts of the cow, I wanted to showcase it in one of its best known dishes, tacos. From being cooked in a pressure cooker, the tongue becomes tender and steaklike, at just about half the price. I didn't want to throw out the delicious braising liquid, so for fun, I popped it into the blender to see what would happen. The result was delicious, but oily from the rendered fat. By using a bit of xanthan gum, I was able to turn that beefy broth into something nearly as thick and lip-smacking as queso, but with no cheese in sight. The amount of queseaux is more than necessary for the recipe, so don't hesitate to dip tortilla chips into the warmed goo for a snack the next day.
Add the tongue, garlic, onion, beef broth, chipotles in adobo and salt to a stovetop pressure cooker. Follow the manufacturer's instructions for locking on the pressure cooker lid set over high heat. Pressure cook at high pressure for 30 minutes. Follow the manufacturer's instructions for quick-releasing the pressure, then unlock the lid and use tongs to remove the tongue, reserving the cooking liquid. Allow the tongue to cool to the touch, running under cool water in a colander. Use your fingers or a paring knife to trim away the skin. Cube the meat and season with kosher salt. Put a 12-inch cast-iron pan over medium-high heat and add the oil. Heat until hot, then add the seasoned tongue and sear until evenly browned, about 5 minutes.
Meanwhile, blend the cooking liquid with the xanthan gum, creating your "queseaux."
Build your tacos: tortillas, seared tongue, diced onion and cilantro. Serve alongside the lime wedges, "queseaux" and salsa.