In a large pot, melt the butter over medium heat. Add the minced shallots, diced celery, and garlic. Sauté until the vegetables are softened and fragrant, about 5-7 minutes.

Add Liquids

Pour in the dry sherry and cook for an additional 2-3 minutes, allowing the alcohol to evaporate. Add the fish stock or chicken broth and bring to a simmer.

Incorporate Crab and Cream

Stir in the heavy cream and crab meat. Let it simmer gently for about 10 minutes, allowing the flavors to meld. Season with salt and black pepper to taste.

Blend the Bisque

Using an immersion blender, blend the bisque until smooth. Alternatively, transfer it to a blender in batches, blending until smooth, then return to the pot.

Serve

Ladle the bisque into bowls. Drizzle with basil oil, and garnish with celery leaves. Serve with crostini on the side.