Serves 4
In a pot, add beans and cover with cold water by 2’’. Soak overnight. Drain beans and cover again with 2’’ of fresh water. Bring a boil, reduce to a simmer, and cook until beans are tender, about 1 ½ hours. Drain beans and return to pot. Add sugar and cook on low until it has dissolved. Transfer mixture to a food processor. Pulse until a thick paste forms with half of beans still intact.
In a medium bowl, combine rice flour, wheat flour, and tapioca starch. Add ¾ cup warm water and mix well. Allow to rest 15 minutes. Add ¾ cup cold water. Bring 1 cup of water to a boil and add cane sugar. Stir until dissolved. Cook until caramel is golden brown and bubbly, about 1 minute. Add caramel to flour mixture and whisk well. Pour mixture into 4 ramekins.
Add 3 inches of water to a wok and bring to a boil. Add 2 ramekins to each bamboo steamer and stack on top of wok. Cover for 2 minutes and cook. Add 1 heaping tablespoon of bean paste to each ramekin. Cover and cook and additional 15 minutes. Remove ramekins from steamer and allow to cool. Remove cakes from ramekins and serve.