Sift flour, cornflour, and baking powder together and stir in sparkling water and sesame oil to form a smooth batter.
Gently mix banana pieces into the batter until they are completely coated.
Heat vegetable oil in a deep heavy-bottomed saucepan until a breadcrumb sizzles and browns immediately.
Deep-fry the bananas until golden brown and drain on paper towels.
Cook sugar, water, and sesame seeds over low heat until sugar melts, then boil until reaching a light caramel color.
Dip fritters into hot caramel, plunge into iced water, then drain on a wire rack.
Serve the warm fritters immediately with a scoop of vanilla ice cream.