Boudin (everywhere else spells it incorrectly) is different depending on where you are in the state, but it's all the same basic concept. However, some places will do whatever is necessary to keep their recipe completely secret. For those that don't know, it's a regional delicacy here in South Louisiana, but some will turn up their noses knowing how it's made (my wife did for years). Here's a simple recipe to get you started and then you can tweak the spices as you see fit...
Take a 4lb pork roast, 1lb of pork liver (you can substitute beef liver, but it will change the flavor), 4-6 cloves of garlic and 1-2 large onions (rough chop) and boil it until the roast is falling apart (take the liver out of the pot when it's done, reserve the onion, garlic, and the liquid). Let it cool enough to work with, then go over to your grinder and using a coarse grind plate, grind & mix the roast, liver, garlic, and onion (one pass). It should be slightly chunky, not smooth, hence the coarse plate and only one pass.
Make a pot of rice (2C long grain), cut up 1 bunch of green onion, put your hog casings in water (synthetic casings don't work and alter the flavor dramatically). For those of you that can't have or don't like rice, you can substitute 4C of cauliflower that has been destemmed then pulsed in the food processor and steamed (it should still be firm, but not raw).
In a big mixing bowl (or a sausage mixer if you have one), put the meat/onion/garlic mixture and add in the rice at about a 75% meat - 25% rice ratio. While doing this, add in your seasoning mix (Tony Chachere's, Zatarains, Slap Yo Mama, or some other creole/cajun seasoning...from Louisiana, not something that claims to be creole or cajun seasoning but is actually mostly paprika) to taste. The seasoning mix will get knocked way down by all the meat and rice, so be generous with it. Add in your green onion as well. Check your texture as you're mixing and add the reserved liquid as needed. It's hard to tell via internet the proper consistency, it should stick together in your hand, but if any is off your palm it should fall back into the pot.
Once all this is done, prep your sausage stuffer and start pressing out some links. About 8-10in long links is about right. Once it's all stuffed, you can freeze it, steam it, or toss it on the smoker or grille. You don't need to cook it again (it's all already cooked), you just need to thoroughly warm it up.
IF there is no creole/cajun seasoning around you, mix up the following...
1/4C salt
1/4C granulated garlic
1/4C finely ground black pepper
2T paprika
2T onion powder
2T ground white pepper
1T cayenne pepper