To make the lamb shoulder, gently warm 2.5 litres/4¼ pints water in a saucepan large enough to hold the lamb. Add the saffron and then the other spices, the bay, the ginger and garlic and salt. Bring to a simmer then gently lower the lamb into the pot, top with half the onions and cover with a lid. Simmer gently for 5–6 hours, until the meat is falling off the bone, keep an eye on the liquid level and add a little more each time it has reduced by half.
Preheat the oven to 200C/180C Fan/Gas 6 and place the butter and oil in a roasting tin.
Remove the lamb from the saucepan and transfer to the roasting tin. Baste the lamb all over with the butter and oil then roast for 30–40 minutes, until the lamb is crisp.
Add the remaining onions to the lamb poaching liquid, bring to the boil then simmer for about 30 minutes, to make a sauce. Remove from the heat.
Meanwhile, to make the bulgur wheat salad, heat 2 tablespoons of the oil in a large frying pan and gently fry the onions for about 30 minutes, until golden and caramelised. Drain on kitchen paper.
Bring a saucepan of water to the boil and blanch the courgette for 1 minute, remove from the water and place in a bowl of cold water. Drain and pat the courgette dry.
Heat the remaining oil in a frying pan and fry the courgette until golden-brown. Set aside.
Bring another saucepan of water to the boil and add the celeriac, butter and nutritional yeast, reduce the heat to a simmer and cook for 20 minutes, or until the celeriac is tender. Remove from the heat and set aside.
Add half of the caramelised onions to a large saucepan, with the bulgur wheat, courgettes and chicken stock. Bring to the boil, then reduce to a simmer, cover with a lid and cook on the lowest heat for 15 minutes. Add the sultanas, stir, then continue to cook for another 10 minutes until the stock has been absorbed and you can fluff the bulgur with a fork. Mix the celeriac through the bulgur wheat and check for seasoning.
To serve, toast the peanuts in a dry pan over a medium heat for 5 minutes.
Load a serving platter with the bulgur wheat and scatter the nuts and remaining caramelised onions, spring onions and herbs on top. Remove the lamb from the oven, pull the meat from the bone and pile it onto plates to serve with the salad and poaching liquid sauce.