1. Preheat the oven to 400°F. Place the pork butt in a large baking dish. Coat it evenly with the vegetable oil and season with salt and pepper. Roast until caramelized, about 35 minutes.
2. Add the caramelized pork to a large stock pot, along with the ham hocks, sage, celery, onion, carrot, molasses, allspice, cloves, black pepper and cold water (either 12 cups or enough to cover the ingredients). Cover the pot and bring to a boil over high heat. Lower the heat to a simmer and cook until the meat is fork tender, about 3 hours more.
3. Strain the solids into a colander set over a large pot or heatproof bowl. Reserve 12 cups of the remaining liquid (if you have less than 12 cups, add some salted water to make up the difference).
4. Discard the vegetables and finely chop or puree the meat. Add the meat and the 12 cups of liquid to a pot and bring to a boil. Lower the heat to medium, then slowly whisk in the cornmeal and buckwheat flour. Once it binds to become a tight mush, transfer the mixture to an ungreased 9-by-13-inch baking dish. Smooth the top and refrigerate for 24 hours, until completely set.
5. After 24 hours, remove the scrapple from the baking dish and slice it into 2-by-¼-inch squares. At this point, you can put any extra squares in zip-top bags, freeze them and then defrost once ready to use.
6. Dredge slices of fresh or defrosted scrapple in flour. Melt your butter or bacon fat in a cast iron or heavy-bottomed pan over medium heat and add your scrapple squares in a single layer, working in batches if needed. When they are golden brown and crispy (about 4 minutes per side) remove the scrapple pieces from the pan and pat them dry with paper towels. Serve with your favorite accompaniments.