Preheat the oven to 200ºC fan
Combine the oil and garam masala and mix to a paste
Place the lamb into a roasting tin and make slashes all over, then rub all over with the garam masala paste and season well with salt
Place into the oven and roast for 1 hour 30 minutes
Add the shallots, aubergines, garlic and limes around the lamb then pour over the stock and return to the oven
Turn the temperature down to 170°C and roast for a further 30 minutes, then give the vegetables a stir and return to the oven for 30 minutes
Remove from the oven and allow the lamb to rest for 20 minutes before slicing and serving with the onions and aubergines