Preheat oven or toaster oven to 400°F/200°C degrees. If using an air fryer, set to 370°F/185°C on "bake" if yours has that specific function.
Combine egg, half the breadcrumbs, chopped herbs, green onions, lemon juice, Old Bay seasoning, mustard, ¼ teaspoon coarse salt, cayenne and several grinds of black pepper in a large bowl. Put the remainder of the breadcrumbs into a separate shallow bowl. Discard fish skin.
Crumble fish into bowl, sifting to uncover any bones. Mix thoroughly.
Coat a cookie sheet with cooking spray or olive oil. Form the fish mixture into small cakes, about 1/3-inch thick. Dip both sides of the fish cakes into breadcrumbs and place on the cookie sheet.
In an oven or toaster oven, bake at 400°F/200°C degrees for about five minutes, then broil for about 90 seconds until golden. Turn off broiler, remove sheet from pan and carefully flip cakes. Bake another five minutes and then broil until the top is golden another 90 seconds.If using an air fryer, bake for eight minutes, turning halfway through. Serve warm.