For soft polenta, bring milk and 800ml water to the boil in a large saucepan, season to taste, add polenta in a thin stream, whisking continuously. Reduce heat to low, stir continuously with a wooden spoon until polenta is smooth (30-40 minutes), then stir in cream, parmesan and butter, keep warm.
Meanwhile, remove beaks and eyes from cuttlefish with a sharp knife (discard), reserve tentacles. Rinse inside of bodies, cut into 5cm-triangular pieces. Heat butter and oil in a large frying pan over medium-high heat, add guanciale, garlic, fennel seed, and chilli, sauté until starting to brown (3-4 minutes). Add cuttlefish, reserved tentacles and parsley and sauté until just cooked (2-4 minutes). Season to taste, serve immediately with polenta.
Note Guanciale is cured pig's jowl or cheek,
available at Italian butchers and delicatessens.