Bring the chicken broth to a boil in a large pot. Add the asparagus and corn; stir. Add the sherry and white pepper; stir. Cook for 3 minutes, or until the asparagus is bright green in color.
Stir the cornstarch mixture into soup, adding it gradually, until lightly thickened. The soup should not be as thick as a sauce.
Once the soup is thickened, add the crabmeat and scallions. Stir well, and serve immediately.