In a large pot, melt the butter over medium heat. Add the onion, celery, and carrot, cooking until the vegetables are soft, about 5-7 minutes. Stir in the garlic and cook for an additional minute.

Add the lobster and tomato paste

Stir in the lobster meat and tomato paste, cooking for another 2-3 minutes until everything is well combined.

Deglaze with sherry

Pour in the sherry, scraping the bottom of the pot to release any browned bits. Let it simmer for about 2 minutes until slightly reduced.

Add fish stock

Add the fish stock to the pot and bring to a boil. Reduce the heat and let it simmer for 20 minutes.

Blend the soup

Using an immersion blender, blend the soup until smooth. If using a regular blender, allow the soup to cool slightly before blending in batches.

Add cream and season

Return the soup to the pot (if blended in a regular blender) and stir in the heavy cream. Season with salt, black pepper, and fresh thyme to taste. Heat through without boiling.

Serve

Ladle the bisque into bowls and garnish with chopped chives before serving.