Special equipment: meat grinder and sausage stuffer
In a large bowl, combine the pork, garlic, sage, salt and crushed red pepper. Run the meat mixture through the meat grinder outfitted with the die with the largest holes. Repeat so that all of the meat goes through the grinder twice.
Place half of the meat mixture in the bowl of a standing mixer equipped with the paddle attachment. Add half of the water and half of the Parmesan and beat on medium-high for 3 to 4 minutes. Repeat this process with the remaining meat, water and cheese.
Make, cook and eat a test patty to make sure the sausage is delicious.
Attach the sausage-stuffing attachment to the meat grinder, keeping the grinder blade and die in place also.
Keeping the sausage casing very wet, slide a manageable length onto the sausage stuffer. Place a generous amount of the prepared sausage mixture into the grinder pan. Give the casings a slight bit of resistance by holding onto the sausage stuffer with your three last fingers and letting the casing slip through your thumb and forefinger. Turn the machine on a medium-low speed and fill the casings, being careful to avoid any air bubbles. To get the feel for stuffing the sausages, you might have to do a couple tries. The first couple might be too loose or too tight; that's ok--think of them as the first pancake (the one that never comes out right that you have to throw away).
Twist the casings to create sausages that are even in size. Tie each with butcher's twine to keep them nicely sealed. Prick the sausages with a pin or skewer all over to allow steam to escape while cooking (you don't want to have a blowout).
Preheat a grill or saute pan. Cook the sausages until cooked through, 7 to 8 minutes on each side. Serve immediately or at room temperature.
This is a BIG batch of sausage, but it freezes really well. If you have casings left over, pack them in salt and store them in your fridge--they will last a REALLY long time.