Split lengthwise and make a small groove in both halves.
Stuff about 1 Tbs red bean paste between each 2 banana halves.
Join halves, then cut each banana into 1 1/2 inch (4 cm) sections.
Mix the flour and tapioca starch in a bowl.
Add water gradually and mix into a smooth batter.
Mix in the baking powder. (The consistency of the batter should be rather thick.)
Heat the wok, add oil, and heat to 350Â° F (177Â° C).
Dip the banana sandwiches in the batter.
Fry 7 to 8 pieces at a time until golden brown, about 6 to 8 minutes.
Drain, sprinkle sugar on top, and serve.