Put 2.5 litres of water and a really good pinch of sea salt into your largest pan, then pop in 1kg of lamb neck fillet (bone in) and bring to a simmer over a medium heat for 45 minutes, skimming away any scum from the surface. Meanwhile, peel 750g of swede, 2 carrots, 2 potatoes, 1 parsnip and 1 onion, and trim 1 leek, 1 bulb of fennel and 2 sticks of celery (reserving any leaves), then cut it all into 1cm cubes. Add all the vegetables to the pan with the lamb, put the lid on slightly askew and cook for a further 30 minutes, until the meat and veggies are lovely and tender. Remove the lamb fillet from the pan and, once it’s cool enough to handle, strip all the meat off the bone (discard the bone). Either dice or pull apart the meat, and return it to the pan. Shred 200g of leafy cabbage and add it to the broth for the final 5 minutes of cooking time, then season to taste. You can serve the cawl immediately, sprinkled with any reserved celery leaves. Alternatively, keep it until the next day, when the flavours will have developed even further.