Preheat your oven to grill as high as it will go.
Drizzle the shoulder with olive oil on each side before seasoning generously with flaky salt. Place on a baking tray and then into the oven under the grill to brown the top. When properly caramelised, remove from the oven.
Turn oven to 160 degrees fan.
Pour a litre of the milk into a pan and warm up gently until steaming but not scalded. In the meantime, chuck the onion quarters and garlic into the tray with the bay leaves and rosemary. Peel the zest from the lemons and add to the tray with the juice of one whole lemon. Pour the milk over the top, so the tray is filled, but the shoulder is still peaking through the top, a great expression from Fergus Henderson is that you’re looking for “alligators floating in a swamp.” Season with salt and lots of black pepper, then cover with a sheet of baking parchment and seal completely with tin foil before placing in the oven for about 5 hours until the hogget is so tender you can pull it apart with a spoon. About 1/2 way through have a check and top up with a little more milk.
When ready, pull the meat off the bones and mix through the molten veg and curdled gravy. Serve with buttery mash and nutmeg with lots of the sauce and make sure everyone gets some of the lemon zest.