Preheat the oven to 425 degrees. Line a baking sheet with aluminum foil, and spray the foil with nonstick cooking spray.
Lay the fillets on the baking sheet, and season them with salt and pepper.
In a medium bowl, combine the bread crumbs, oil, parsley, lemon juice, garlic, kosher salt, and mustard, and mix them together well with a fork. Press an equal amount of the bread crumb mixture onto the top of each fillet.
Bake the fish until it is white and flakes easily in the center, about 10 minutes. (For a browner topping, broil it for the final 2 minutes of cooking.) Sprinkle the fish with additional lemon juice before serving, if desired.