Purée the mango, banana and coconut milk in a blender until rich and smooth. Pour the mixture into lolly moulds and freeze overnight.
The next day, whizz the granola slightly in a small food processor to remove any large lumps (or tip into a bowl and bash with the end of a rolling pin), then tip into a bowl.
Melt the chocolate in a heatproof bowl set over a pan of simmering water, making sure the base of the bowl isn’t in contact with the water.
Remove the lollies from their moulds. Dip the tops one at a time in the chocolate, then into the granola. Place on a tray lined with baking parchment to set – they will set very quickly. Eat immediately or freeze until needed.