Combine the marinade ingredients except lamb and butter in a bowl.
Rub the marinade onto the lamb and set aside for two hours.
Preheat your oven to 200°C.
Place lamb in a roasting tin and cook for ten minutes.
Baste with marinade and roast for five more minutes until cooked to preference.
Drizzle with melted butter and rest in a warm place.
Boil mint leaves in water, refresh in iced water, and drain.
Blend mint with chutney ingredients in a food processor until smooth.
Mix mango salad ingredients together in a bowl.
Carve lamb and serve with salad and chutney.