Pick over the crabmeat for cartilage and return to the refrigerator. Melt the butter in a 4-quart saucepan. Add the celery, green onion, carrot, garlic, and ginger. Cover and simmer over low heat until the vegetables are tender, about 4 to 5 minutes. Whisk in the flour. Gradually add the broth and milk, bringing the mixture to a boil while stirring constantly. Add the cayenne, nutmeg, salt, white pepper, lemon peel, cream, and sherry. Heat thoroughly. Stir in the crabmeat and cook until it is heated through. Do not boil. Serve immediately.