Cook the fish fillets in 1 1/2 cups water (360 ml) with salt until they are tender. Let cool, then flake the fish and reserve the cooking liquid.

In the oil, sauté the onion and serrano pepper. Add the tomatoes and cook to make a sofrito.

Add the flaked fish, white wine, and about 1 cup (240 ml) of the reserved cooking liquid. Cook over low heat until the mixture is seasoned and most of the liquid has evaporated, or to your preferred consistency.