4 large slices white sandwich bread , torn into 1-inch pieces
2 tablespoons unsalted butter , melted
table salt & ground black pepper to taste
2 tablespoons fresh parsley, minced
1 small shallot , minced (about 2 tablespoons)
1/4 cup plus 5 tablespoons all-purpose flour
2 large eggs
3 tablespoons mayonnaise
1/2 teaspoon paprika
1/4 teaspoon cayenne pepper (optional)
1 1/4 pounds skinless cod, haddock or other thick white fish fillet (1 to 1 1/2 inches thick), cut into 4 pieces
Cooking spray
Lemon wedges