Finely dice the onion, celery, and carrot to create a uniform mirepoix base.
In a medium pot, melt the ghee over medium heat and sauté the onion, celery, and carrot until softened and translucent, about 6-8 minutes.
Stir in the tomato paste, sea salt, black pepper, and dried thyme, cooking for another 2 minutes until the paste darkens slightly.
Pour in the dry sherry to deglaze the pan, scraping up any browned bits from the bottom.
Add the seafood stock and bring the mixture to a gentle simmer for 10 minutes to meld the flavors.
Using an immersion blender or high-speed blender, puree the soup until completely smooth.
Place the Greek yogurt in a small bowl and stir in two tablespoons of the warm soup to temper it, then whisk the yogurt mixture back into the pot over low heat.
Gently fold in the lobster meat and simmer for 3-4 minutes until the lobster is heated through but still tender.
Ladle the bisque into a bowl and garnish with freshly chopped chives before serving.