For the lamb, preheat the oven to 200C/400F/Gas 6.
Place the lamb shoulder onto a roasting tray. Pierce it all over about 20-30 times using a sharp knife, making incisions in the skin about 0.5cm/¼in deep. Insert the garlic slices and rosemary sprigs into the incisions.
Transfer the lamb to the oven and roast for 10 minutes, or until beginning to brown.
Reduce the oven temperature to 140C/275/Gas 1.
Pour the lamb stock and red wine over the lamb.
Continue to roast the lamb for two hours, or until the meat is very tender and the cooking liquid has thickened (check the meat and baste it with the cooking liquid every 20 minutes during cooking). Add more stock to the roasting tray if the liquid dries out.
Meanwhile, for the smoked aubergines, heat a frying pan over a high heat until smoking, then reduce the heat to its lowest setting.
Add the aubergines to the hot pan and cook for 20-25 minutes, turning every 4-5 minutes, until the skins are charred and the insides are tender. Remove from the pan and set aside to cool.
When the aubergines have cooled, cut each in half and scoop out all of the flesh (discard the skin).
Blend the smoked aubergine flesh, Greek-style yoghurt, lemon juice and garlic in a food processor to a smooth paste. Cover and chill in the fridge until needed.
When the lamb has cooked, set aside to rest for up to 20 minutes. Skim the fat from the thickened cooking juices left in the bottom of the roasting tray. Set aside.
Meanwhile, for the salad, heat a griddle pan over a medium to high heat. Drizzle over the one tablespoon of olive oil.
Cook the peppers for 4-5 minutes, turning once, or until golden-brown griddle marks appear on each side, then remove from the pan and set aside.
Add the onion rings to the pan the peppers were cooked in and cook for 3-4 minutes, turning once, or until golden-brown griddle marks appear on each side. Remove from the pan and set aside. Keep warm.
Add the courgette slices to the pan the onion was cooked in and cook for 3-4 minutes, turning once, or until golden-brown griddle marks appear on each side. Remove from the pan and set aside. Keep warm.
Add the mushroom slices to the pan the courgette slices were cooked in and cook for 3-4 minutes, turning once, or until golden-brown griddle marks appear on each side. Remove from the pan and set aside. Keep warm.
Add the griddled vegetables to a large serving bowl. Add the beans, cherry tomatoes, basil leaves, rocket leaves and feta cheese and mix well to combine.
Drizzle over the olive oil, to taste, and the balsamic vinegar. Season, to taste, with salt and freshly ground black pepper.
Just before serving, add the boiling water to the meat juices in the roasting tray and stir to combine to make a gravy.
To serve, tear the meat from the lamb shoulder using a fork and divide it equally among four serving plates. Pour over the gravy. Spoon the smoked aubergine and grilled vegetable and white bean salad alongside.
