For the Pork Carnitas:
If using pink salt, combine with the brine. Brine the pork shoulder for 12 hours. Drain the pork and pat dry.
Combine the coriander, cumin, ancho, cinnamon, and chipotle with just enough water to form a paste. Cover the brined pork shoulder with the spice paste and marinate for 24 hours.
Line a deep hotel pan with a rack; put the pork shoulder into the pan and cover with aluminum foil. Cook in a combi-oven at 195°C, 50 percent humidity, and 3 bars of fan, for 8 to10 hours until the meat just starts to pull away from the bone.
Pull the meat off the bone in large chunks, removing the fat and saving the cooking juices. In a large rondeau, caramelize the pork in the pork fat. Remove the pork and roughly chop. Finally, add in some of the cooking juices, rendered pork fat, chopped red onion, and cilantro to taste.
To Assemble and Serve:
Serve Pork Carnitas with fresh corn tortillas, sour cream, and tomatillo salsa.