Place a griddle or cast ion skillet over medium heat. Tear the chiles into large flat pieces and toast them a few at a time, pressing them down with a spatula. When they blister and change color, flip over and toast the other side. Cool and transfer to a coffee grinder reserved for grinding spices. Add the coriander, cinnamon stick, clove, oregano, and peppercorns. Pulverize the spices and sift through a medium-mesh sieve into a large bowl. Add the nutmeg, ginger, paprika, an salt, then stir in the garlic and vinegar. Set up a meat grinder fitted with the coarse grinding plate and the sausage stuffing attachment, or use a sausage-stuffing funnel for the stuffing procedure. Mix together the pork fat, loin, and shoulder and run them through the grinder into the bowl with the spices. Mix the meat and the seasonings briefly but thoroughly with your hands. Cover and refrigerate overnight.
If the castings were packed in salt, rinse them for an hour before using. Run water from the tap through each length of casing to check for leaks; either cut the casing where it leaks or discard the piece (to be useful, a casing should be at least 30 inches long wit no leaks). Thread one end of a piece of casing over the suffer or the funnel mouth, pushing it all the way on but leaving a 3-inch overhang for tying off. Begin feeding the sausage meat through; when it first comes out, clamp off the end so that the sausage expands to a 1-inch diameter. If there is an air bubble, stop the machine and work the bubble out towards the funnel end. Feeding the sausage through the grinder in an uninterrupted flow, slowly move the casing away from the suffer as the sausage fills in a continuous 1-inch diameter link. When the sausage is about 6 inches long, pull off an extra 1 inch of casing and twist several times, completing one link and starting another. Continue until all of the sausage meat has been cased, stopping to thread more casing on as necessary.
Either twist the links several more times to separate them, or tie pieces of string between them. Place on a rack in the refrigerator, uncovered, for about 36 hours or until dry to the touch and somewhat firm. Set a dish underneath to catch drips. Wrap in plastic and again refrigerate until ready to use.
c.1997, M.S. Milliken & S. Feniger, all rights reserved