Asparagus was introduced to the Vietnamese cuisine by the French, so it is not found in many traditional Vietnamese recipes. But today this soup is a popular item on the banquet menu. If fresh asparagus and crabmeat are not available, you can use canned, but fresh ingredients are always preferred by the Vietnamese. Look for lump crabmeat from the body of the crab. The most difficult part of this otherwise simple dish is making sure the egg whites are properly whipped into the soup. The presentation should be that of gentle clouds floating in the soup.