Place the clams in a bowl, add cold water to cover, and set aside.
Rinse the bones, head, or whatever scraps you have from the hake with cold water. Place in a medium pot and add water to cover. Bring to a boil over high heat, reduce the heat to low, and simmer for about 20 minutes. Strain the liquid (called fumet) through a fine-mesh sieve and discard the solids. Set the fumet aside.
Scrub and drain the clams; set aside.
Rinse the hake fillets and pat them dry. Season the skin-free side of each fillet with salt.
In an earthenware casserole or a large sauté pan, heat the olive oil and garlic over medium-high heat. When the garlic starts to “dance,” add the flour and cook, stirring, for about 30 seconds. Pour in the wine and simmer for about 30 seconds to cook off the alcohol. Add 1 cup (240 mL) of the fumet and simmer for about 1 minute.
Add the hake fillets to the pan, skin-side up. Simmer for about 3 minutes. Gently turn the hake fillets over. Add the clams, placing them around the pot, and cook for about 5 minutes. Should the pan begin to look dry, add more fumet.
Sprinkle the parsley over the pan. Remove from the heat and move the pan in a circular motion until the sauce begins to come together and emulsify, 1 to 2 minutes. Taste and adjust the seasoning.
Serve in individual bowls or family-style. You can reserve the remaining fumet for another use.