Cook onion in butter in a Dutch oven over medium heat 5 minutes or until onion is tender.
Stir in flour; gradually add chicken broth, stirring constantly. Add asparagus and potato, and bring to a boil. Cover, reduce heat, and simmer 20 minutes or until vegetables are tender. Let cool slightly.
Puree asparagus mixture in a blender or food processor in batches until smooth, scraping down sides, if necessary. Add milk, whipping cream, and salt, stirring well. Cook over medium heat just until thoroughly heated.
Ladle soup into individual serving bowls. Top evenly with chopped lobster, and sprinkle with toasted almonds.
Note: Substitute cooked crab or shrimp for the lobster, if desired.