Preheat the oven to 180C/350F/Gas 4.
Brush two ramekin dishes with a little melted butter. Add a small amount of sugar to each, turn them to coat the sides and bottom, shaking out any excess.
Heat the coconut milk, flour, cornflour, lime zest and butter in a saucepan over a medium heat for 5-6 minutes, or until thickened slightly.
Put the egg yolks into a bowl and pour the coconut milk mixture over them, whisking continuously until well combined.
In a separate, clean bowl, whisk the egg whites with the sugar until it forms soft peaks when the whisk is removed.
Carefully fold the coconut mixture into the egg white mixture.
Pour the soufflé mixture into the ramekins, level off the tops with a palette knife and place onto a baking tray. Transfer to the oven for 6-8 minutes, or until risen and golden-brown.
To serve, dust with icing sugar using a sieve. Serve immediately.