"A traditional Chinese dessert analogous to rice pudding. The eight treasures refers to the 8 different nutritious ingredients that go into it. It is traditionally eaten on Laba festival (December 8th on the lunar calendar). Ingredients can be easily substituted but just remember there should be 8 main ingredients (for namesake), and you should adjust the time at which the ingredient goes into the pot to ensure everything is cooked just right at the end. Other common ingredients include jujube, chestnuts, dried dates, dried longan meat, other dried fruits, peanuts, almonds, walnuts, melon-seed meat, pine nuts, lotus seeds, sesame seeds, kidney beans, black bean, and many others."
Place red beans into a large container and cover with several inches of cool water; let stand 3 hours to overnight. Drain and rinse.
Combine red beans and barley in a pot; add enough water to fill 1/2 the pot. Bring to a boil, reduce heat to low, cover pot, and simmer until beans and barley are tender, about 1 hour.
Mix rice into bean-barley mixture; add more water if it has all been absorbed. Cook rice mixture for 20 minutes. Add mung beans; cook for 20 minutes.
Mix oats, millet, and tapioca into rice mixture; cook, stirring every 5 minutes, until all the grains are softened, about 20 minutes. Add more water to reach desired thickness of porridge. Stir brown sugar and raisins into porridge; cook for 5 minutes more. Remove pot from heat, stirring occasionally to prevent sticking. Serve hot or chilled.