Puree the prepared mangoes in a blender. Transfer to a bowl. Pour the evaporated milk onto the mango puree, add the sugar and mix well.
In a measuring jug, measure 200ml hot water and add the gelatine (and not the other way round or you will get lumpy bits). Quickly stir until all the gelatine granules have dissolved then add to the pureed mangoes and mix well.
Ladle the mixture into 4 dishes. Place on a tray and refrigerate for at least 1 hour.
When ready to serve, briefly put the dishes in a baking tray with some hot water to help loosen the pudding. Use a flat knife to run round the edges of the pudding, place a plate on top of the dish and quickly invert it – the pudding should fall onto the plate. Squeeze over some of the lime juice, dust with icing sugar and decorate with lime zest and a sprig of mint.
Serve with fresh mango slices and some vanilla ice-cream.