Preheat the oven to 200C/400F/Gas 6.
For the banana fritters, sift the flour, cornflour and baking powder together into a bowl then stir in the water and sesame oil. Add the bananas and gently mix until coated.
Fill a wide pan half full with vegetable oil and heat until hot, or alternatively heat a deep fat fryer to 180C/350F. (CAUTION: Hot oil can be very dangerous. Do not leave unattended.)
Place the bananas into the pan and fry until golden-brown, then drain on paper towels.
For the soufflé, lightly grease four large ramekins with butter, then dust with half the sugar.
Place the egg whites in a clean bowl and whisk to soft peaks. Add the remaining caster sugar and whisk to stiff peaks. Fold in the custard and carefully spoon into the ramekins.
Place the ramekins on a baking tray and immediately transfer to the oven. Bake for 10 minutes, or until golden-brown and risen.
Meanwhile, to make the caramel, place the sugar in a frying pan and heat until all the sugar has melted. Increase the heat and continue cooking without stirring, until the syrup becomes a light caramel colour. Add the sesame seeds and stir well.
Remove from the heat and carefully add one banana fritter at a time to the hot caramel (CAUTION: The caramel will be very hot, take care not to burn yourself). Turn it over with a fork to completely coat the fritter in caramel, then remove immediately and plunge into a bowl of iced water. Remove and drain on a wire rack while cooking the remaining fritters.
Serve the fritters immediately with a scoop of vanilla ice cream, the soufflé and a spoonful of custard.