If using whole lobsters, remove the lobster meat from the shell and set the lobster meat into the fridge. Set the shells aside to add to the soup later.

Heat butter in a saucepan over medium heat. Add the leeks, onion, and cook for 4 minutes or until softened.

Add the celery, thyme, orange zest and the tomato paste. Cook about 5 minutes while stirring occasionally.

Add the broth, lobster shells and salt and bring to a boil. Lower the heat to a gently simmer until the soup is reduced a little, about 30 minutes.

Remove the lobster shells and sprigs of thyme and discard. Add the cream cheese to the pot. Use a stick blender to combine the soup until smooth.

Add the lobster meat (either whole lobster or lobster pieces) into the soup and cook over medium heat for 10 minutes for whole lobsters (or 5 minutes for lobster pieces) or until the lobster is cooked through.

To serve, ladle the bisque into warmed soup bowls with a lobster tail in each bowl.