01 - Melt the butter with the olive oil in a large pot over medium heat. Add the onion, celery, and carrot, and sauté until softened, about 6 to 8 minutes.
02 - Stir in the garlic and cook for 1 minute. Add the tomato paste, Old Bay seasoning, and paprika, stirring frequently, and cook for another 2 minutes.
03 - Pour in the sherry or white wine, scraping up any browned bits from the bottom of the pot. Let simmer for 1 to 2 minutes until slightly reduced.
04 - Add the seafood stock and bay leaf. Bring to a simmer, cover, and cook for 15 minutes to develop depth of flavor.
05 - Remove and discard the bay leaf. Purée the mixture until completely smooth using an immersion blender, or transfer to a standard blender in batches. Return the purée to the pot if needed.
06 - Stir in the whole milk and heavy cream. Bring back to a gentle simmer without boiling to prevent curdling.
07 - Add the lump crab meat and chopped shrimp. Simmer gently for 6 to 8 minutes until the shrimp are pink and cooked through.
08 - Adjust the seasoning with salt and freshly ground black pepper as needed.
09 - Ladle the bisque into bowls. Garnish with chopped parsley and a squeeze of lemon juice if desired.