Dice the lamb and sprinkle on the spice, salt, pepper and mix well. Pre heat a non stick pan, toss the lamb into the flour and brown on high heat from all sides. Meanwhile dice the onion, celery, leeks and chop the garlic, remove the lamb from the pan and add the vegetables with a knob of butter. Once vegetables start to brown add the red wine bring to the boil than pour in the tomato pulp, chopped sun dried tomatoes, lamb and simmer gently. Dice the sweet tomato, toss in olive oil seasoning and roast in the oven until browned. Add the sweet potato to the stew once cooked through and serve with the yogurt and coriander leaves on.