Put the fennel seeds and water in a small saucepan and bring to a boil.
Reduce the heat and simmer for about 8 minutes. Strain and reserve the liquid, about 3 tablespoons. Discard the seeds.
Season the pork with the salt, cayenne, onion powder, garlic powder, black pepper, and the fennel essence. Using your hands, mix well. Grind the pork mixture through a meat grinder fitted with a 1/4-inch die. Or, put the pork mixture in a food processor fitted with a metal blade and pulse several times to coarsely grind the meat. It should not be pureed into a paste.
Either stuff the mixture into prepared 1/2-inch-diameter casings or divide it into small portions. It can be frozen indefinitely.
Yield: about 3 1/2 pounds