Place the pork and the rest of the stock ingredients in a saucepan, and the pork liver in a separate saucepan. Cover with water (at least 4 quarts), then bring to a boil. Reduce heat, skim and simmer until tender, about 1 hour, skimming as necessary.
Remove the meat, discard the vegetables and strain the stock. Continue to boil the stock until it's reduced to about 2 quarts. Remove enough of the stock to have enough liquid to make rice, and cook the rice in the pork stock. Reserve the leftover pork stock, at least 1 pint.
Cook the bacon until crisp, remove it and use it to snack on while you're making the rest of the boudin. Add the onions, green onion bottoms and garlic to the drippings and sauté for a few minutes until the onions are translucent, then add the liver. Cook until the liver is tender. Add about 1/2 cup of pork stock to the pan, and cook for 10 more minutes, until much of the pork stock is reduced.
Put the pork, along with the liver and vegetable mixture, through a meat grinder with a coarse disc, or grind it coarse in a food processor. Transfer the mixture to a large bowl and mix in the green onions tops, parsley, salt, peppers and cooked rice. Adjust seasonings. If it seems too dry, add a little bit more pork stock. It should be moist, but not runny.
For traditional boudin, stuff into sausage casings. Boudin links are generally about a foot long. You can also serve it out of the casing as a rice dressing.
Place in a 350°F oven for 10-15 minutes, until the boudin is heated through and the skin is crackly. Serve hot, with crackers and beer.
(To make boudin sausage balls, do not stuff into casings. Roll each ball into golf-ball sized balls. Dip in milk, roll in seasoned flour, and let sit for 2-3 minutes. When the flour from the first roll-through is damp, roll through the seasoned flour again. Deep-fry until golden brown and crispy. Serve with beer.)