This authentic Spanish seafood recipe calls for Merluza (hake), but because it isn’t easy to find, I substituted halibut.
Other white-fleshed fish such as sea bass will also work. So will salmon: it isn’t particularly Spanish but it is incredibly good when prepared this way.
Preheat the oven to 500F. Rub the halibut with salt and pepper and let stand while you prepare the potatoes. Place the potatoes in a saucepan. Add salted water to cover by 2 inches and bring to a boil. Cook the potatoes until they just begin to feel tender when pierced with a skewer, 25 minutes or longer depending on their size.
Do not overcook. Drain the potatoes and let cool enough to handle, then, cut them into slices. Generously coat a 10-inch ovenproof skillet with oil.
Arrange the potatoes in a slightly overlapping layer on the bottom. Sprinkle the potatoes with salt.
Place 1/3 cup olive oil and the garlic in a small skillet and heat over medium-low heat until the oil simmers and the garlic just begins to take on color, about 2 minutes.
Add the chile and stir for 15 seconds. Using a slotted spoon, transfer the garlic and chile to a bowl.
Add the vinegar to the skillet and immediately cover it, as the oil will splatter. Cook, covered, for the flavors to blend, 2 minutes, turn off the heat, and let stand.
Pour some of the vinaigrette over the potatoes and scatter some of the fried garlic and chile over them.
Arrange the halibut fillets on the potatoes, pour the remaining vinaigrette on top, and scatter the remaining garlic and chile over them. Bake the fish until it just flakes when tested with a fork, 10 to 12 minutes depending on the thickness.
Sprinkle the parsley on top and serve.
Serves 4 to 6