Scoop them into a blender along with the tomatillos (and any juice on the baking sheet), onion and a scant teaspoon salt. Process to a coarse puree. In a microwavable bowl, sprinkle the potatoes with a tablespoon of water, cover with plastic, poke a few holes in the top and microwave at 1. Heat the oven to 3.
In a medium (4- quart) heavy pot (preferably a Dutch oven) set over medium- high, heat enough oil (or one of its stand- ins) to coat the bottom. When the oil is hot, dry off the meat with paper towels, sprinkle it generously with salt and lay it in the pan (lay the cubed shoulder in an uncrowded layer). Brown on all sides (this takes 5 to 1. Let it reduce and concentrate, stirring frequently, for about 4 minutes. Then roughly chop the poblano and add it to the pot along with the potatoes. Finally, stir in the broth (or water) and epazote. Return the meat to the pot, cover and slide it into the oven. When the pork loin reaches 1. When ready to serve, reheat the sauce over medium, taste and season it with salt (usually about 1 teaspoon). Slice the meat, lay the slices overlapping on 4 warm deep dinner plates, then spoon the sauce and potatoes over and around it.
If using cubed pork shoulder, braise until tender (that takes about 1 hour), season the sauce with salt, then spoon the delicious mixture into deep plates. Either one benefits from a fresh garnish of cilantro leaves.