Carefully clean, rinse and pat dry the hake. Season the fillets lightly with salt. Heat the oil over medium-high heat in a large, heavy frying-pan.
Add the garlic and cook for about five minutes, until the garlic just begins to color.
Sprinkle the flour over and mix thoroughly for about one to two minutes. Add 225ml of water, clam broth or juice, parsley, wine and salt to taste. Decrease the heat to medium and cook sauce, stirring occasionally for five minutes, until the sauce is slightly thick or just barely coats the back of a wooden spoon. You can add more cold water to loosen up the sauce if necessary.
Lightly salt the hake fillets and add them to the pan, skin side up, in a single layer. Cook the hake fillets in the sauce for two minutes, swirling the pan constantly and sliding the pan on and off the fire until the hake fillets give off some of their gelatin and emulsify with the rest of the sauce. Turn the hake fillets once and cook for another two to three minutes on the other side, until the fish is opaque but not overcooked. The sauce should be very light green, slightly thick but still loose and light. Serve immediately.