Step 1

Mix the fish coating ingredients in a tray or plate that is large enough to hold one fish fillet.

Step 2

Mix the sauce ingredients in a big bowl. Stir to mix well.

Step 3

Score the fish by slicing a 1” (2.5 cm) crosshatch pattern across the flesh. If using skin-on fish, cut to the skin but not through it. If using skinless fish, cut through about 2/3 of the fillets so the fillets won’t fall apart.

Step 4

Prepare a roasting rack over a big tray, for the cooked fish fillets.

Step 5

In a deep-sided pan that’s large enough to hold one fish fillet, heat 1” (2.5 cm) of oil over medium-high heat until it reaches 375°F (190°C). If you’re using smaller fish fillets, you can use as little as 1/2” (1.2 cm) of oil, as long as it covers 2/3 of the fish.

Step 6

Only coat as much fish as you can fry at a time. Place the fish skin-side-down in the tray with the cornstarch mixture. Use a spoon to add more mixture on top. Carefully lift the fillet using your hand to shake off the extra cornstarch and make sure there’s cornstarch between the diamond cuts.

Step 7

As soon as the fish is coated, glenty lay it, flesh-side-down, into the heated oil. Cook without touching until the bottom turns golden, 3 minutes for smaller fish, and 4 minutes or so for larger fish. Flip and cook the other side, for another 2 to 3 minutes.

Step 8

Once done, transfer the fillet to the tray lined with the rack to drain the extra oil.

Step 9

In a medium-sized frying pan, heat 1 teaspoon of oil over medium heat until hot. Add the ginger and garlic. Stir to release the fragrance, 30 seconds or so.

Step 10

Add the onion. Stir a few times.

Step 11

Stir the sauce mixture again to thoroughly dissolve the cornstarch and pour it into the pan. Stir and cook to bring the sauce to a boil.

Step 12

As soon as the sauce starts to thicken, add the bell peppers. Stir a few times until the sauce thickens. Immediately transfer the sauce into a bowl.

Step 13

Plate the fish on a large tray or on individual serving plates. Add the sauce along with the pepper and onion onto each fillet. Garnish with toasted sesame seeds, if using. Serve immediately.