Melt the ghee in a large pot over medium heat, then add the diced onion, celery, and minced garlic, sautéing until the vegetables are soft and translucent.
Stir in the tomato paste and cook for 2 minutes to deepen the flavor profile before pouring in the dry sherry to deglaze the pan.
Add the seafood stock and bring the mixture to a gentle simmer for 10 minutes to allow the aromatics to meld.
Use an immersion blender to process the soup until it reaches a completely smooth and uniform consistency.
In a small bowl, whisk the arrowroot powder into the heavy cream until no lumps remain, then stir this slurry into the simmering soup to thicken.
Fold in the cooked lobster meat and heat for 3-4 minutes until the lobster is warmed through, being careful not to boil the cream.
Season with sea salt and black pepper, then serve in warm bowls garnished with finely chopped fresh chives.