1. Preheat the oven to 170ºC/325ºC/gas 3. In a pestle and mortar, bash 4 peeled garlic cloves, half the rosemary leaves and a pinch of salt and pepper into a paste, then muddle in a good lug of oil. Stab the lamb ten times, then stick your finger in each hole and massage the marinade in and all over. Peel and quarter the onions and place in a snug-fitting roasting tray (this is important), with the lamb on top. Add 50ml of water, cover tightly with tin foil and cook for 3 hours. Remove the foil, pour away all the fat (save as dripping – see page 158) and add another 200ml of water to the tray. Cook for 1 hour more, or until the meat falls away from the bone, adding another good splash of water, if it starts to dry out.
2. Meanwhile, peel the potatoes, halving any larger ones, and parboil in a large pan of boiling salted water for 12 minutes. Drain and shake to fluff up, then tip into a roasting tray. Strip in the rest of the rosemary leaves, drizzle with oil, bash and add the remaining unpeeled garlic cloves, and toss with salt and pepper. Place in the oven under the lamb tray for the final 1 ½ hours. With 20 minutes to go, pick and very finely chop the mint leaves, scrape into a small jug and mix with the sugar, vinegar and 1 tablespoon of boiling water. Chop the bacon and cook in a large frying pan on a medium heat until golden. Trim, roughly slice and throw in the cabbage with a splash of water, cook for 10 to 15 minutes, or until softened, then season to perfection.
3. Remove the lamb from the oven, transfer to a platter and cover. Put the tray on a medium heat on the hob and stir in the flour, then pour in 600ml boiling water and any lamb resting juices. Stir well and simmer until you’re happy with the consistency. Pour the gravy into a jug, or if you prefer it smooth, pour and push it through a sieve first. Quickly blanch the peas in a pan of boiling water for a couple of minutes, then drain. Serve everything in the middle of the table, with all the usual trimmings.
4. Tip: If you’re not going to use all the leftover lamb within 2 or 3 days, simply portion it up and freeze for making meals in future weeks. Defrost in the fridge for 24 hours before cooking.