Cook slowly in a heavy saucepan or double boiler.
Melt 2 tablespoons butter in saucepan. Add sherry and bring to a boil. Add lobster and remove from heat. In separate saucepan melt remaining 3 tablespoons butter. Saute mushrooms, onion, and green pepper until soft. Sprinkle with flour and stir until blended. Drain sherry from lobster and add to sauteed vegetables. Heat to simmer. Beat egg yolks and cream, add ¼ cup of hot sherry, blend with whisk, and return mixture to saucepan. Stir mixture slowly over low heat. Add lobster and heat. Season with salt and pepper.