Melt the butter in a 5 quart dutch oven.
Saute the onions until translucent.
Stir in the sherry.
Sprinkle the flour over the onions and stir well to combine.
Cook for a few minutes until the flour starts to darken.
Add the chicken broth a half cup at a time, stirring well after each addition.
Allow the bisque to thicken before adding more broth.
Stir in the tomato paste, salt, pepper, Worcestershire sauce, celery seed and Old Bay.
Stir in the cream and reduce the heat to a low simmer.
Allow the bisque to continue to thicken and for the flavors to meld.
Add the crab and adjust the seasonings.
The bisque is ready when the crab is heated through.
To serve, ladle into shallow bowls and mound some of the reserved crab meat in the center. Garnish with a little parsley. Serve more sherry on the side to add to the soup if desired.