This fragrant soup brings Thai flavors—coconut, lemongrass and ginger – to a fresh, bright, versatile asparagus soup. It can easily be made vegetarian or vegan, works at any time of year (though it is especially great in the spring) and is both filling and healthy. We love to have it for lunch on a casual week day or for an appetizer for a fancy dinner. With a soup like this you just can't go wrong! —Fig Test Kitchen
Cook onion in 3 tablespoons butter or oil in a 6-8 quart heavy pot over moderately low heat, stirring until softened, about 10 minutes.
Add lemongrass and ginger and continue cooking until vegetables are soft, about 3 minutes.
Add asparagus pieces, salt and pepper, then cook over medium heat, stirring frequently for about 5 minutes.
Add coconut milk and 5 cups of broth. Simmer, covered, until asparagus is very tender, about 15 minutes.
Puree soup in batches in a blender or with a immersion blender until smooth, transferring to a bowl after blending if using a blender since you will need to do it in several batches (use caution when blending hot liquids) and return to pot. If the soup is too thick, add up to another cup of broth, and cook for about five minutes, or until the soup is warm.
Add lemon juice, and serve with a garnish of chives or cilantro. (Soup may be prepared a day in advance. If making ahead, add the lemon juice after reheating.)