For the sauce, heat olive oil in a heavy based pan. Brown the pork all over. Add the butter, onion, garlic, anchovy, basil leaves, bay leaf, chilli and fennel seeds. Cook over a low heat and stir in the wine and stock. Let it bubble vigorously for a couple of minutes to burn off the alcohol. Stir in the passata. Reduce heat and simmer for 1 hour, uncovered until the pork is tender.
Remove the pork from the sauce and chop finely, return meat pieces and remove from heat.
Meanwhile, in a large mixing bowl, combine ingredients for sausage except for the caul fat. Use your hands to mix everything together well.
Stretch out the mince into a long sausage shape and wrap in the caul fat.
Grease a round baking dish and lay sausage in a coil. Drizzle with olive oil. Transfer to a preheated oven at 180C for 12 to 15 minutes or until cooked.
To cook the polenta, heat the oil in a large, heavy based pan. Add the onion, garlic and thyme and sweat gently for 5 minutes or until they are soft.
Season with salt and pepper. Add the stock to the pan and bring to the boil. Pour in the polenta in a slow steady stream, whisking all the vigorously until the mixture begins to boil, then lower the heat to a brisk simmer. Cook for 5 – 10 minutes, stirring with a wooden spoon from time to time, until the mixture thickens and becomes smooth and creamy. Remove the pan from the heat and stir in the chopped herbs and cheese. Taste and adjust the seasoning if necessary – you may find the cheese is salty enough.
Serve sausage on a bed of polenta topped with a generous amount of the meat ragout.