Pour the oil into a heavy-bottomed lidded saucepan or casserole placed over a medium– high heat. Add the pork mince, fry to colour for 5 or 6 minutes, decant and set aside.
Put the pan back on the stove, with the heat slightly lower than before. Add the butter to the oil and juices still in the pan, then sauté the diced fennel and celery for around 8 minutes so they’re glistening and beginning to soften (but not brown – reduce the heat further if necessary). Add the garlic and fennel seeds, stir and cook for 1 minute more, before returning the pork to the pan.
Turn the heat up, wait for 30 seconds then push a portion of meat to one side to reveal the base of the pan and pour the wine or vermouth in. Allow this to boil and bubble for 1 minute before reducing the heat to medium and adding the milk, Parmesan rind, thyme and nutmeg. Place a lid on top, slightly ajar, and simmer very gently for 1 hour. The milk might curdle slightly – that’s fine, just stir from time to time to ensure it’s not sticking to the bottom, and to encourage the sauce to come together.
Once the time is up, check the seasoning, adding salt, pepper, more nutmeg and/or thyme to taste.
Put a large saucepan of salted water on to boil and cook your pasta according to the packet instructions. At this point remove the ragù from the stove to cool while the pasta cooks (it tastes best when not piping hot).
Once the pasta is cooked to al dente, drain through a colander, reserving a few ladles of cooking water. Return the pasta to the saucepan, add three or four ladles of ragù to it, plus a ladle of reserved cooking water and stir constantly for 20–30 seconds to ensure a loose and creamy glaze to the pasta. Add a splash more cooking water if needed.
Serve, spooning the remaining ragù over each portion of pasta, plus a little dusting of Parmesan and fennel fronds.