Sauté the base
Warm olive oil in a Dutch oven over medium heat. Stir in celery, carrot, and onion; cook 5 minutes until glossy. Add garlic; cook 60 seconds.
Bloom the flavor
Mix in tomato paste, paprika, and cayenne. Stir 2 minutes so everything turns brick‑red and fragrant.
Build the roux
Sprinkle flour over veggies; stir nonstop 2 minutes to lose the raw taste.
Whisk in stock
Pour broth little by little, whisking to dodge lumps. Bring to a gentle bubble, then drop heat and simmer 12 minutes until slightly thick.
Finish with cream + seafood
Stir in sherry (if using) and cream; keep heat on low so it never boils. Fold in shrimp and crab; warm 5 minutes.
Season & serve
Taste, add salt and pepper, ladle into warm bowls, and shower with fresh herbs. Pass crusty baguette for swooping every last silky drop.