For the marinade, place all the ingredients in a food processor and process until smooth.
Put the chicken thighs into a large mixing bowl and pour over half of the marinade, use your hands to mix well. Cover and refrigerate overnight. Reserve the other half of the marinade in the fridge.
Preheat the oven to 180°C.
Transfer the chicken into a medium oven dish – the chicken thighs must fit snuggly in the oven dish. Pour over the reserved marinade to evenly coat the chicken and bake until the chicken is cooked through, for 45 – 60 minutes.
Mix the diced mango with the rosemary and top over the chicken and serve while still hot.