Melt butter and add olive oil. Sauté onion, garlic, and celery until soft and translucent. Deglaze the pan with dry sherry for added flavor.
Sprinkle flour, whisking until a thick paste forms. Gradually add seafood stock, whisking to remove lumps. Add bay leaf, spices, and bouillon powder, mixing well.
Remove the bay leaf, taste the soup, and season with salt and pepper according to your preference. The flavors should be perfectly balanced.