How to Make It
Heat oven to 400° F. In a food processor, pulse the bread and 2 tablespoons of the oil to form coarse crumbs. Spread on a rimmed baking sheet and bake, tossing once, until golden, 6 to 8 minutes.
Meanwhile, heat the remaining tablespoon of oil in a large saucepan or Dutch oven over medium-high heat. Add the leeks and cook, stirring occasionally, until tender, 4 to 5 minutes. Add the wine and cook until reduced by half, about 2 minutes more. Add the clam juice and 1½ cups water and bring to a boil.
Add the fish and clams to the saucepan and simmer gently, covered, until the fish is opaque throughout and the clams have opened, 4 to 6 minutes. (Discard any that remain closed.)
Stir in the half-and-half, ½ teaspoon salt, and ¼ teaspoon pepper and cook until heated through, 1 to 2 minutes. Serve sprinkled with the parsley and bread crumbs.