Remove the lobster meat from the shell, and chop meat; set aside. Place lobster shell in a large pot with water, clam juice, and bay leaf. Cook over medium-low heat for 30 minutes. Strain liquid and reserve stock; discard solids.
Melt butter in a large saucepan over medium heat. Add onion and celery and saute for 3 minutes. Sprinkle flour over mixture in pan and cook for 1 minute, stirring frequently. Add reserved stock, milk, cream, tomato paste, salt and pepper and cook, stirring constantly, on medium for 10 minutes to thicken. Stir in lobster meat and sherry and serve immediately. Makes about 4 cups
For A Christmas Eve Snack: Prepare bisque on the morning of Christmas Eve, and cool to room temperature. Cover and store in the refrigerator until ready to serve. Warm in the microwave or in a saucepan on stove top.