Preheat the oven to 180°C.
Put the chicken legs into a baking tin. Cut the onion into 4 wedges and tuck these between the chicken pieces. Brush them with the oil then season with salt & pepper. Put the tin in the oven.
Meanwhile, peel the mango and cut the flesh into chunks. Put the mango and its juice in a food processor together with the garlic, ginger, honey, lime zest & juice and chilli (if used). Whizz until you get a textured paste.
After 20 minutes of baking take the chicken out of the oven and pour away the pan juices. Coat each piece well with the glaze using a silicon brush. Tuck the lime halves between the chicken. Bake for 20-25 minutes, until golden and cooked through, turning the chicken pieces once.
Serve the chicken with the pan juices and some coriander leaves scattered all over.