Heat olive oil in a large pot over medium heat. Sauté the chopped celery, carrot, and onion for about 5 minutes until softened. Add minced garlic and cook for another minute.
Stir in tomato paste, paprika, and cayenne pepper. Cook for 1-2 minutes to caramelize the tomato paste and bloom the spices.
Sprinkle flour over the vegetables and stir for 2 minutes to create a roux. Slowly pour in the seafood or chicken broth, whisking to avoid lumps. Bring to a simmer.
Simmer the bisque for 10-12 minutes until it thickens. Stir in sherry (if using) for extra flavor.
Lower the heat to medium-low and add the heavy cream. Stir in the chopped shrimp and crab meat, cooking for 5 more minutes until heated through.
Season with salt and black pepper to taste. Ladle into bowls and garnish with fresh herbs like parsley, chives, or dill.
