1. In a bowl,mix together the soy sauce,bean paste,shao hsing,cumin,chilli,five-spice and sugar. Take a heavy,deep roasting tray large enough to fit the lamb shoulder. Rub the marinade all over the meat,cover the tray with cling film and leave to marinate for a few hours or,better still,overnight in the fridge.
2. Preheat the oven to 150C. Remove the cling film from the lamb and add 250ml water to the roasting tray. Cover the tray tightly with aluminium foil,then place in oven and roast for two hours. Turn the oven down to 110C and cook for a further four hours,checking every so often and adding a little more water if the tray becomes dry.
3. For the last hour remove the foil and drizzle the two tablespoons of grapeseed oil over the lamb and continue to cook for the last hour of roasting to crisp up the skin.
4. While the lamb is roasting,make the Sichuan sauce and the coriander and mint paste. Transfer the lamb to a deep dish,and pour the Sichuan sauce over the top. Finish the dish with the chilli oil and ground Sichuan pepper. Serve withflatbread andcoriander and mint paste.
Find more of Andrew McConnell's recipes in theGood Food Favourite Recipes cookbook.