In a food processor, puree the onions, fennel, celery, and garlic until it becomes a coarse paste. Season with salt and give a sprinkle of crushed red pepper.
07When the sausage is roasted, remove it from the oven and coarsely chop.08Coat a wide, deep pot with olive oil and add the pureed veggies. Cook the veggies until they start to brown, about 10 minutes. Add the tomato paste and cook for 1 to 2 minutes. Add the white wine and reduce by half. Toss in the chopped sausage and the tomato puree. Taste and season with salt, if needed. Bring to a boil and reduce to a simmer and simmer for 20 minutes.09Remove the polenta from the pan and cut into desired shapes. Coat a nonstick saute pan with olive oil and bring to medium-high heat. Once the pan is hot and starting to smoke just a little, add the polenta shapes. Cook the polenta on both sides and finish by sprinkling with the Parmigiano.10Transfer a few polenta cakes to a plate and top with the sausage sauce. Sprinkle with more grated Parmigiano.11Place the pork shoulder in a bowl and keep cold until ready to use. Fill a large bowl with ice and place the bowl with the pork shoulder on top.12Season the pork with garlic, salt, fennel seed, crushed red pepper, and coriander. Mix to combine well.13Grind the pork shoulder twice through a grinding disk with large holes. Grind the meat into the bowl sitting on ice.14Cook a small amount of the meat mixture to test for seasoning. Add more spices and salt, if needed. Thoroughly mix in a splash of cold water. Allow the seasoned pork to chill on ice or in the fridge before stuffing into the casing.15Replace the grinder attachment with the horn. (Be sure to thoroughly clean the attachment area before proceeding.) Rub oil onto the horn, and then put the casing on, leaving a few inches of slack at the end.16Stuff the casing, tie off the ends, and prick the sausage with a pin or the tip of a knife.17Refrigerate the sausage until ready to cook.