4 large slices sandwich bread , torn into 1-inch pieces
2 tablespoons unsalted butter, melted
2 tablespoons minced fresh parsley leaves
1 small shallot , minced (about 2 tablespoons)
¼ cup plus 5 tablespoons unbleached all-purpose flour
2 large eggs
2 teaspoons prepared horseradish (optional)
3 tablespoons mayonnaise
½ teaspoon paprika
¼ teaspoon cayenne pepper (optional)
1 ¼ pounds skinless cod or haddock fillet, or other thick white fish fillet
Adjust oven rack to middle position and heat oven to 350 degrees. Pulse bread, melted butter, 1/4 teaspoon salt, and 1/4 teaspoon pepper in food processor until bread is coarsely ground, eight 1-second pulses. Transfer to rimmed baking sheet and bake until deep golden brown and dry, about 15 minutes, stirring twice during baking time. Cool crumbs to room temperature, about 10 minutes. Transfer crumbs to plate; toss with parsley and shallot. Increase oven temperature to 425 degrees.
Place ¼ cup flour on second plate. In a pie plate or square baking dish, whisk eggs, horseradish (if using), mayonnaise, paprika, cayenne pepper (if using), and 1/4 teaspoon black pepper until combined; whisk in remaining 5 tablespoons of flour until smooth.
Spray wire rack with nonstick cooking spray and place in rimmed baking sheet. Dry fish thoroughly with paper towels and season with salt and pepper. Dredge 1 fillet in flour; shake off excess. Using hands, coat with egg mixture. Coat all sides of fillet with bread crumb mixture, pressing gently so that thick layer of crumbs adheres to fish. Transfer breaded fish to wire rack. Repeat with remaining 3 fillets.
Bake fish until instant-read thermometer inserted into centers of fillets registers 140 degrees, 18 to 25 minutes. Using thin spatula, transfer fillets to individual plates and serve immediately with lemon wedges.
Nutrition information per 4 ounce fillet
Calories 235, Fat 7.5g, Protein 21g, Carbohydrates 18g, Fiber 1g, Cholesterol 115mg, Sodium 188mg