Trim Fish Fillet (1 pound) of your choice and set the trimmings aside.
Cut the fish fillets into large pieces. Peel Shrimp (12 ounce) and remove tails. Save the shell aside.
In a stock pot, heat Extra-Virgin Olive Oil (1/2 cup) and saute Onion (1). Add the fish trimmings, shrimp shells, half the Tomato (1) and Fresh Thyme (3 sprig).
Add Fish Stock (1 quart), White Wine (1 cup) and simmer for 20 minutes. Season with Salt (to taste), Cayenne Pepper (to taste) and Garlic Paste (to taste) to taste, simmer another 2 minutes
Strain the solids from the stock, squeeze to extract all the stock/flavor.
Add remaining Tomato (1) and Potato (1 cup), if using, simmer 3 minutes.
Add in the fish, Capers (2 ounce), Fresh Parsley (2 tablespoon) to the fish soup, simmer 3 more minutes, remove from heat, taste and adjust seasoning.