Lamb is such a fantastic thing to cook because you can’t go too wrong with the cooking time – no matter whether you overcook it or take it out slightly too early, it will still be wicked! Using a rolled shoulder means it will be much easier to carve, so do go for this cut.
The celeriac in the potato smash adds an impressive twist. You can prepare the veggies in advance, stacking them in the different compartments of a steamer, ready to go.
Preheat the oven to 180°C/350ºF/gas 4 and get yourself a large roasting tray. Season both lamb shoulders with salt and pepper, and rub them all over with olive oil. Place into the tray and throw in the garlic cloves, onion quarters and rosemary sprigs. Cover with tinfoil and cook in the oven for 3½ hours.
Meanwhile, break the kale, cabbage and greens into leaves and cut out any tough stems. Stack the veggies in a vegetable steamer, with the broccoli at the bottom and the delicate kale leaves at the top. Season each layer with salt and pepper and top with a knob of butter. Put to one side.
Cut the celeriac into chunks the same size as your potato pieces. Place the potato and celeriac into a big pot and cover with cold, salted water. Bring to the boil and simmer for 15 minutes until cooked through. Drain well and add the butter and hot milk. Season with salt, pepper and the nutmeg. Smash everything up with a potato masher – this is a smash, so you want a bit of texture in there, nothing too smooth. Put to one side.
After 3½ hours, take the lamb out of the oven, remove the foil and pop it back in for a final 30 minutes or until meltingly tender. If you’re serving this as part of a dinner party, now’s the time to serve your starter.
After 4 hours, remove the meat to a wooden board and cover with tinfoil to keep it warm. Allow it to rest while you see to your veggies and gravy. Bring the water in your steamer to the boil and steam the veggies for 6 minutes. Place the roasting tray, with all the juices from the lamb, on the hob over a medium heat. (Have a look in the tray – if there’s loads of fat, then skim some off with a spoon.) Remove the rosemary sprigs and garlic skins, then squash the onion and garlic with a fork. Add the flour and give it a good stir to get rid of any lumps of flour, then pour in the stock and stir again. Allow to reduce for 5 minutes and, when nice and thick, pass the gravy through a sieve into a gravy boat. At the same time, reheat the smash on a gentle heat for a few minutes, stirring constantly.
To serve, get everyone up to the table and put the wooden board in the middle – the lamb will smell and look wonderful. Carve it into slices and let everyone help themselves to some smash and steamed veggies. I love this kind of eating, it’s lovely and relaxed, with everyone chatting and passing cutlery and plates around!