Prepare the Lobster Stock
Heat olive oil in a large pot over medium heat. Add the lobster shells, onion, carrot, and celery. Sauté for 5-7 minutes, or until the vegetables are softened.
Stir in the garlic and tomato paste, cooking for another minute. Deglaze the pot with white wine, scraping up any browned bits from the bottom.
Add water, bay leaf, and thyme. Bring to a boil, then reduce the heat and simmer for 30 minutes.
Strain the stock through a fine mesh strainer, pressing on the solids to extract all the liquid. Set aside.
Cook the Lobster Meat
Chop the lobster meat into bite-sized pieces and set aside for later.
Make the Bisque Base
In the same pot, melt butter over medium heat. Stir in the flour to create a roux, cooking for 2 minutes.
Gradually whisk in the lobster stock, ensuring there are no lumps. Bring the mixture to a simmer and cook until slightly thickened, about 10 minutes.
Blend the Bisque
Use an immersion blender to puree the soup until smooth. Alternatively, blend the soup in batches in a regular blender and return it to the pot.
Finish the Bisque
Stir in the heavy cream and sherry. Add the chopped lobster meat and season with salt and pepper. Simmer gently for 5 minutes to heat through.
Serve
Ladle the bisque into bowls and garnish with fresh parsley. Serve hot with crusty bread or oyster crackers on the side.