Preheat oven to 350°F / 177°C / Gas mark 4.

Pat fish dry, then season with half of the salt and pepper.

In a small, shallow bowl, mix flour with remaining half of the salt and pepper. Set aside.

Place beaten egg in a separate small bowl. Set aside.

Add panko breadcrumbs to a third small bowl, along with herbs, if using, then set aside.

Dip filets into flour, shake off excess, then dip into egg and lastly into panko. Place fish, breaded side up, on a clean plate.

Heat a cast iron pan over medium high heat. Add enough oil to cover the bottom and come about 1/8" up the side of the pan.

Carefully place fish, breaded side down, into pan and cook until deep golden brown, about 5 minutes. Then flip fish over and place on sheet pan.

Bake for an additional 6 - 8 minutes, depending on the thickness of your filets. Fish should easily flake apart with a fork when cooked through.