Loaded with asparagus and crab, Vietnamese Fresh Asparagus and Crab Soup (Sup Mang Tay Cua) is elegant looking and delicately flavored. Vietnamese consider it special-occasion fare because it features asparagus, a pricey ingredient introduced by the French as an imported canned good. In Vietnamese, asparagus is măng tây, literally “French bamboo,” an apt name as both asparagus and bamboo shoots grow quickly.
Resourceful Viet cooks often maximize the asparagus flavor by adding the spears and their canning liquid to the soup. But the taste is nonetheless rather flat, and canned asparagus is mushy. To achieve a strong asparagus flavor, I use fresh asparagus to prepare the soup.
Asparagus declines in sweetness as soon as it is harvested, so choose only the freshest. Spring is asparagus season, and at farmers’ markets the spears are sold within twenty-four hours of being cut. To keep them fresh, stand them in a tall container filled with about an inch of water. (If the ends look dry, trim them first.) Refrigerate the container; there is no need to cover it with plastic.