Melt butter in the top of a boiler set over boiling water
Add the celery and onion, cook 2 minutes
Stir in the flour and cook 1 to 2 minutes
Whisk int the warm milk and cook, whisking often, until the mixture thickens, 10-12 minutes
Stir in the cream, salt, worcestershire sauce, mace, white pepper and cayenne pepper. Just before servings, stir in the crab meat, stir 1 tbsp sherry into the saoup. Serve at once.
