Add the chopped veg and a sprig of rosemary to the slow cooker. Sprinkle over 3 tbsp of cornflour.
Using a small sharp knife, poke holes in the lamb at regular intervals. Press in a small sprig of rosemary and a slice of a garlic clove into each hole. Season the lamb well with salt and pepper.
Place the lamb shoulder into the slow cooker, and pour the stock and wine down the sides, taking care not to wash the seasoning off of the top of the lamb. Check that the lamb is sat in the liquid (approximately a half to two-thirds covered), and if not dig out some of the vegetables and place them around the side of the meat so that it sits lower. If required, add more stock and wine using the ratio of two parts stock to one part wine. You do not need to submerge the lamb in liquid.
Cook on low for five and a half hours or four on high (see recipe notes regarding cooking times as it can vary depending on your model of slow cooker). Once cooked, remove the lamb, place it a roasting dish, and cook in the oven for 20 minutes at 190°C. Whilst the lamb is cooking in the oven, prepare the gravy.
Following cooking the lamb there will be a lot of fat sat on top of the gravy in the slow cooker. Use a meat baster to remove it (transfer it to a bowl and bin it once cooled, don't put it down the drain).
If you have a sear and stew slow cooker, transfer the pot to the hob, or transfer the contents of the slow cooker to a pan if not. Add a further tbsp of cornflour. Do this by removing a few tbsp of liquid into a mug, stirring in the cornflour to create a slurry, and stirring it back into the gravy.
Bring the gravy to a boil, then reduce to a simmer. Add a tsp of blackcurrant jam, then check the thickness, and reduce further, if required.
Check the seasoning, then serve by pouring through a colander into a gravy jug, or without a colander if you prefer to keep the vegetables in the gravy.
How long will it take to cook?
The cooking times stated are for the slow cooker mentioned in the equipment list. Cooking times vary a lot across different models of slow cooker.Older slow cookers with ceramic pots will heat much slower than newer models with metal pots, and therefore will have a longer cooking time.To be sure, check regularly after five hours of cooking.
How will I know when the lamb is cooked?
You'll be able to pull the meat apart easily with a fork (check in a few places), and it'll be easy to pull out the flat shoulder bone. It's even quite likely that the bone will start to fall out when you lift it from the slow cooker!Every piece of meat is slightly different and may require slightly more or less cooking.
I'm running out of time and it's still not cooked!
We've all been there! Remove the lamb and a little liquid from the slow cooker and transfer to a roasting dish. Cover with foil and cook at 160C until the meat is tender.