“Much yummier than I thought it would be. I loved the buttered breadcrumb crunch on top!” —Jack, recipe tester, age 9
Adjust oven rack to middle position and heat oven to 300 degrees. Line rimmed baking sheet with aluminum foil and set cooling rack inside baking sheet. Spray rack with vegetable oil spray.
In 12-inch skillet, melt butter over medium heat. Add panko, garlic, salt, and pepper and cook, stirring often with rubber spatula, until lightly browned, 3 to 5 minutes.
Turn off heat. Transfer panko mixture to medium bowl. Stir in parsley and let cool for 10 minutes.
Meanwhile, in small bowl, whisk together mayonnaise, egg yolk, and lemon zest.
Use paper towels to pat fish dry. Use back of small spoon to spread mayonnaise mixture evenly over top of each fillet.
Working with 1 fillet at a time, coat top of each fillet with panko mixture. Place fillets, crumb side up, on greased rack in baking sheet. Wash your hands.
Dip mayonnaise-coated side of fish into panko mixture. Press crumbs so they stick to fish.