Heat a saute pan over medium high heat.
Add sesame oil when pan is hot.
Meanwhile, combine¼ cup flour and ¼ cup cornstarch in a bowl, add ¼ teaspoon salt and ⅛ tsp ground black pepper. Set aside.
Wash fish fillet and dry with paper towels.
Cut into big bite-size pieces.
Lightly season fish with salt and ground black pepper.
When oil is hot, put fish fillet and fry until golden brown then flip to cook the other side.
While fish is frying, make the sauce by combining all sauce ingredients in a bowl. Mix well. Set aside.
Take the fish out of the pan. Pour the sauce into the pan.
Turn up heat to high and let sauce cook until reduced in by a third or half and the consistency is slightly thickened.
Put the fish back and gently stir to mix so sauce coats the fish pieces evenly.
Add sesame seeds. Turn off heat and transfer fish in a platter.
Sprinkle roasted seeweeds on top (this is optional). Enjoy!