When making sausage I use percentages, like bakers do. This way the recipe can be immediately adjusted to the amount of product you're trying to produce or the amount of meat you have. The following are my notes from a sausage class I taught at the farm where we buy our pigs. Among the interesting people attending were a fellow who told me he has lived for the last 15 years on roadkill and a couple just back from Peru, who gave me this:
Look closely at that package. I don't think I'll be drinking this myself but I guess it's a fun thing to have as a curiosity. Onto the formulas
2-3 % salt is the norm. Fat should be between 15-25%. A good pork shoulder usually has the right ratio. If it seems lean to you, add back fat. Many commercial products have up to 50% fat. The seasoning percentages are for total meat and fat. Example: 4# meat + 3/4# fat (64 oz X .2=12.8oz). Total mass for seasoning is 4.75# or 76 oz. For the Italian formula below this equals 1.5 oz of salt and fennel seed, 1.5 oz fresh chopped garlic or .75 oz garlic powder, and .375 oz chile flakes. The smaller amounts can be converted to grams to make measuring easier. There are 28 grams per oz so 42 grams each salt, fennel and fresh garlic, or 21 grams garlic powder, 10 grams chile flakes.
2% fennel seed
2% garlic or 1% garlic powder
.5% red chile flakes
1 jalapeno per 2# meat
.25 C red wine vinegar per 2# meat
1% ancho chile
.375% black pepper
1 bunch cilantro per 2# meat
1% black pepper
.25% red chile flakes
1% black pepper
.375% red chile flakes
.5 C water per 5# meat
I usually grind everything together to help with the distribution of the spices. Your grinder should be cold, your meat should be cold. I put both the grinder parts and the cubed meat in the freezer until I'm ready to grind. If the meat and grinder are warm, the mixture will be mushy and crushed, not ground.
The next step is quite important. Mix well. You really want to work the mixture and force a semi-emulsification. Otherwise when you go to cook these the fat will exit immediately and you'll be left with a crumbly, dry, flavorless sausage. For a fully emulsified sausage like a frankfurter, you'll take a bit of ice water and combine that with the meat mixture in your food processor and run the machine until the mixture is gummy.
Many grinders come with a stuffer attachment so you can grind and stuff in one pass. These usually go too fast for me and I'd rather have the control that stuffing by hand affords. Unfortunately that means investing in a sausage stuffer, which is essentially a large cylinder with a screw-driven pusher on the open end which forces the mixture into the stuffing horn, over which you have put a casing. Casing the sausage and tying them is my favorite part of the process (well, other than the eating) so I wouldn't be without one but for the home sausage enthusiast it might be a bit much. If you don't want to deal with casings you can certainly for the sausage into patties, or alternately, roll into a log in plastic wrap, tie the ends well, cover with aluminum foil and poach gently to make the sausage shape. Or use the stuffer attachment on your grinder. I beleive Kitchen-Aid has one.
For casings the most practical for home use are regular pork casings. These are the small intestine of a pig. Your butcher should be able to order you some. For larger sausages like cotechino you'll need what they call hog middles. These are also what chitterlings are made from and to some have a strong smell. For really large sausages like braunschweiger, mortadella, cervelats, etc you'll need hog or beef bung which is just what you think it is.
All natural casings should be well rinsed, commercial varietites mostly to remove the salt in which they are packed. Put one open end over the tap of your sink and run the water through. Place over the stuffing horn like you're putting on a condom, being careful not to let air get inbetween the casing and the horn, tie one end in a simple knot and you're ready to go. As you extrude the sausage mixture be careful of air bubbles, this is less crucial on fresh sausages (ones you'll eat in a few days) than it is fermented sausages like salami but it's still good practice to keep your sausages bubble free. If you see a major pocket, prick it with a needle or a push pin. Once all your mixture has come through the stuffer, tie the other end. Don't make the sausage too tight if you intend to tie them, otherwise they have a tendency to break.
The way I tie is really easy, but too complicated for me to describe by writing, so you'll just have to find me and get a demonstration if you want to learn that part of it.