In a large pot, heat olive oil over medium heat. Add onion, celery, and carrot, and cook until softened, about 5 minutes. Stir in garlic and cook for an additional minute until fragrant.

Mix in tomato paste, paprika, cayenne pepper (if using), and a pinch of salt and black pepper. Cook, stirring constantly, for about 2 minutes.

Sprinkle flour over the vegetables and stir until fully incorporated. Cook for another minute to remove the raw flour taste.

Gradually pour in broth while stirring to avoid lumps. Bring to a simmer, then reduce heat to maintain a gentle simmer. Cook for 10 minutes, stirring occasionally.

With an immersion blender, or in batches using a standard blender, puree the soup until smooth. Return to the pot if using a standard blender.

Stir in heavy cream and simmer for another 10 minutes until slightly thickened.

Add crab meat and shrimp to the bisque. If using sherry, stir it in now. Cook for 5 minutes or until seafood is heated through, keeping a gentle simmer to prevent curdling.

Taste and adjust seasoning with additional salt and black pepper as needed.

Ladle into bowls, garnish with fresh herbs, and serve immediately.