Cook the tongue sous-vide style according to manufacturer's recommendation for weight, time and temperature (Karrie cooks hers for 24 hours at 140 degrees).
Remove the tongue to a plate and reserve any cooking juices. Peel, dice and sauté the tongue in the olive oil until slightly crispy and browned.
Add the reserved juices and the chilies in their sauce to the pan and heat. Serve the meat on corn tortillas with chopped onion and cilantro.