This recipe has been adapted from "Cooking by Hand" by Paul Bertolli.
Cut pork and back fat into 1-inch chunks, and place on a baking sheet. Cover with parchment-lined foil, and transfer to the freezer until very cold and almost frozen. Using a meat grinder fitted with a 3/8-inch plate, grind pork and back fat together into a large chilled bowl. Change to a 3/16-inch plate, and grind half of the mixture again. Transfer all of the mixture to refrigerator until cold.
Meanwhile, cut pork skin into 2-inch pieces. Bring a medium saucepan of water to a boil. Add pork skin, and cook until it offers little resistance to the point of a knife, about 1 hour. Drain, and rinse pork skin under cold running water. Using a meat grinder fitted with a 1/8-inch plate, grind pork skin. Place ground skin on a plate, and refrigerate until well chilled.
Remove chilled pork, fat, and skin from refrigerator. Break skin into small pieces. Add to a large roasting pan with salt, black pepper, sage, cayenne pepper, garlic, anise seeds, and dextrose. Mix vigorously with a large spatula, alternately cutting through mixture with the edge of the spatula and turning it over until well-blended, about 5 minutes. As you mix you will notice the meat grow firm and compact.
Tie a knot at the end of hog casing to prevent any of the sausage mixture from coming out. Fit the casing onto a sausage stuffer, and stuff the sausage mixture into it. Twirl off to roughly 4 1/2-inch lengths. Using thin kitchen twine, tie off sausages to prevent them from untwirling. Poke sausages to release any air. Hang to dry in a warm, dry place until sausages lose their surface moisture, then refrigerate. The sausages may be well wrapped and frozen for up to 3 months.