Melt butter in a non-stick frying pan over medium-high heat. Add brown sugar. Cook, stirring, for 1 minute or until sugar dissolves. Add bananas. Reduce heat to medium. Cook for 2 to 3 minutes or until warmed through. Remove from heat and cover to keep warm.
Place milk, coconut milk and vanilla in a saucepan over medium heat. Cook, stirring constantly, for 5 minutes or until hot (donot allow to boil). Remove from heat
Whisk egg yolks, cornflour and caster sugar in a heatproof bowl until well combined. Pour hot milk mixture over egg yolk mixture, whisking constantly.
Return mixture to saucepan over low heat. Cook, stirring constantly, for 8 minutes or until custard thickens and coats the back of a wooden spoon (do not allow custard to boil as it might curdle).
Pour hot custard into serving bowls. Spoon over caramelised bananas. Sprinkle with sesame snaps. Serve.