Dissolve the brown sugar in the boiling water. Once the sugar is dissolved, add in the cold water to bring down the temperature.
In a large mixing bowl, add rice flour and make a well in the center. Stir the brown sugar water and stir to combine. Once combined, knead dough in the bowl for five minutes and shape into a ball. Dough should be the consistency of play dough, add more flour or water if need be to adjust consistency.
Roll the dough into a log and then divide dough into 12 even pieces. Dust hands with a little rice flour and form each piece into a ball roughly the size of a large walnut.
With the palm of your hands, flatten dough ball into a disk. Place a quarter of a teaspoon of red bean paste and a piece of banana in the center of each of the disks. Gather sides toward the center and pinch close. Gently roll in the palms of your hands to reshape into a ball. Repeat with remaining balls. Once all balls are filled and formed, roll in sesame seeds to coat thoroughly.
Heat 7.5cm of oil in a pot or wok to 180°C, or until a piece of dough browns in 15 seconds. Deep fry the sesame seed balls, a few at a time, until the sesame seeds are golden and the balls float to the surface; about three to four minutes. Remove from oil with a slotted spoon and drain on paper towels.
Best served warm.