1 Heat the oven to 450F. Arrange 2 oven racks in the top and bottom third of the oven. Line 2 baking sheets with foil and coat with olive oil (about 1 tablespoon per baking sheet) or with nonstick cooking spray.
2 Prepare the potatoes: Quarter the potatoes lengthwise, then cut each quarter in half again so you get 8 spears from each potato. In a bowl, toss the potatoes with 2 tablespoons of the oil and 1/2 teaspoon salt. Spread the potatoes on the baking sheet with their wedges pointing up, if possible, so the cut sides are exposed (some may not stand; that’s OK).
3 Roast the potatoes: Roast the spears on the lower rack in the oven for 40 minutes. Rotate the pan partway through (after 20 minutes of cooking) and use a wide metal spatula to stir the potatoes. At this point, it’s fine if the potatoes fall on their sides; the sides touching the pan will become extra-crispy and golden.
4 Toast the panko: Once the potatoes are in the oven, start on the panko and the fish. To toast the panko, warm a heavy skillet over medium high heat. Add the panko (no oil needed), and lower the heat to medium. Slowly toast the panko, stirring frequently, for 10 to 15 minutes or until a deep golden brown.
Remove the skillet from heat. Stir the olive oil, 1/2 teaspoon salt, and 1/2 teaspoon black pepper into the panko breadcrumbs until they are well coated. Transfer the crumbs to a shallow bowl.
5 Prepare the fish: Cut the fish into large strips (“fingers”) or big 3-inch pieces, however you prefer. Rub all the pieces with the remaining tablespoon of olive oil.
6 Coat the fish with panko: Press the fish into the panko so the pieces are coated all over. Set the fish on the second baking sheet, spaced slightly apart.
7 When the potatoes are 15 to 20 minutes away from being done, bake the fish: Cook thick (2-inch) fish fillets for 15 to 18 minutes and thinner (1 1/2-inch or thinner) fillets for 10 to 13 minutes, or until the fish is firm and the coating is starting to brown. Err on the side of caution and do not over-bake.
7 Serve the fish and chips: Arrange fish and potato spears on plates, sprinkle with parsley, serve with lemon and tartar sauce.