PreparationMake rémoulade: Pulse all rémoulade ingredients in a food processor until combined, then transfer to a bowl. Make fish: Preheat oven to 350°F with rack in middle. Stir together parsley, horseradish, mustard, garlic, and zest. Gradually stir in panko, then drizzle with 1/3 cup olive oil and gently stir. Pat fish dry and arrange, skin side down, on a large platter. Brush flesh with 1 tablespoon oil, then season with 1/2 teaspoon salt and 1/4 teaspoon pepper. Gently pat about 1/2 cup panko mixture evenly onto each fillet. Heat 1 tablespoon oil in a 12-inch nonstick skillet over medium-high heat until hot, then sauté fillets in 2 batches, crumb side down first, carefully turning once with a large spatula, until golden on both sides, about 6 minutes total per batch. Transfer to a large shallow baking pan. (Fish will not be fully cooked.) Wipe skillet clean and add remaining tablespoon oil for second batch. Bake fish in oven until just cooked through, about 5 minutes. Serve with rémoulade. Cooks' note:Rémoulade can be made 1 day ahead and chilled, covered. Bring to room temperature before serving.
PreparationMake rémoulade: Pulse all rémoulade ingredients in a food processor until combined, then transfer to a bowl. Make fish: Preheat oven to 350°F with rack in middle. Stir together parsley, horseradish, mustard, garlic, and zest. Gradually stir in panko, then drizzle with 1/3 cup olive oil and gently stir. Pat fish dry and arrange, skin side down, on a large platter. Brush flesh with 1 tablespoon oil, then season with 1/2 teaspoon salt and 1/4 teaspoon pepper. Gently pat about 1/2 cup panko mixture evenly onto each fillet. Heat 1 tablespoon oil in a 12-inch nonstick skillet over medium-high heat until hot, then sauté fillets in 2 batches, crumb side down first, carefully turning once with a large spatula, until golden on both sides, about 6 minutes total per batch. Transfer to a large shallow baking pan. (Fish will not be fully cooked.) Wipe skillet clean and add remaining tablespoon oil for second batch. Bake fish in oven until just cooked through, about 5 minutes. Serve with rémoulade. Cooks' note:Rémoulade can be made 1 day ahead and chilled, covered. Bring to room temperature before serving.