Warm Vietnamese sweet soups may be rich and thick, like the preceding recipe, or light and clear, like this one. Here, buttery lotus seeds are paired with longans, a Southeast Asian fruit similar to lychees. During cooking, the dried longans give off a slightly smoky vanilla scent, which is underscored by the vanilla extract. My father swears that this soothing soup helps him sleep soundly. For me, the draw is the interplay among texture, taste, and fragrance.
Lotus seeds normally require long simmering, but they quickly reconstitute when boiled with baking soda, as is done here. (The alkalinity and salt content of baking soda speeds the cooking.) When shopping for the lotus seeds, choose slightly opened ones that have had their bitter green centers removed. If you can’t tell from the packages whether they have been removed, choose one of the higher-priced brands. Dried longans resemble giant raisins and are often shelved near the lotus seeds in Chinese and Vietnamese markets. Look for both of them in the same aisle where you find dried mushrooms and beans.
This Vietnamese Dessert from Into the Vietnamese Kitchen: Treasured Foodways, Modern Flavors by Andrea Nguyen