Here’s a way to get every penny’s worth out of lobsters.
Crush lobster shells into small pieces. Place in soup kettle along with stock, salt and pepper, and parsley. Bring just to a boil, reduce heat, and simmer, partially covered, 2 hours. Strain through cheesecloth. Reserve broth, discard shells. Melt butter in second kettle. Saute onion until soft. Sprinkle with flower and blend with whisk. Slowly add lobster broth, stirring constantly. Remove from heat, add cream, and reheat. Do not boil.