Combine pork, salt, sugar, pepper, garlic, and sherry and marinate 24 hours. Fill a large bowl with ice and place another bowl inside. Grind pork through a medium die into second bowl. Place pork into a mixer and emulsify on medium speed for five minutes. Add vinegar and mix for 2 more minutes. Using a sausage stuffer, pipe sausage into casings. Slow poach for 3 to 4 hours at 180°F without boiling until internal temperature reaches 150°F. Place sausage into a cool water bath until cool. Hang in refrigerator for up to one month.