In a large pot over medium heat, melt the grass-fed butter until it begins to foam.
Add the diced onion, celery, and carrot, sautéing for 5-7 minutes until the vegetables are tender and translucent.
Stir in the minced garlic, tomato paste, dried thyme, sea salt, and black pepper, cooking for another 2 minutes to develop the aromatics.
Pour in the dry sherry to deglaze the pot, using a wooden spoon to scrape up any flavorful browned bits from the bottom.
Add the seafood stock and bring the mixture to a gentle simmer, allowing it to cook for 10 minutes to meld the flavors.
Use an immersion blender to purée the soup directly in the pot until it is completely smooth and velvety.
Stir in the heavy cream and the cooked lobster meat, heating through for 3-4 minutes while ensuring the bisque does not reach a boil.
Ladle the hot bisque into a bowl and garnish with finely chopped fresh chives before serving.