For the fish:
12 ounces cod fillet(340g, rinsed clean, pat dry and cut into 1-inch cubes)
3 cups canola oil (for frying)
¾ cup all-purpose flour
¼ teaspoon baking powder
1 tablespoon cornstarch
½ teaspoon salt
⅛ teaspoon turmeric powder
⅛ teaspoon white pepper
¼ teaspoon sesame oil
⅔ cup cold seltzer or club soda
For the sweet and sour sauce:
¼ cup red onion(cut into a 1-inch dice)
¼ cup red bell peppers (cut into a 1-inch dice)
¼ cup green bell peppers (cut into a 1-inch dice)
1 tablespoon ketchup
3/4 cup canned pineapple chunks
¾ cup pineapple juice from the can
2 ½ tablespoons red wine vinegar
⅓ cup water
¼ teaspoon salt
2 tablespoons sugar
1 1/2 tablespoons cornstarch (mixed into a slurry with 2 tablespoons water)
Make sure your fish fillet is clean and pat dry to ensure your fried fish gets really crispy. Heat 3 cups of oil in a small pot (to conserve oil) to 380 degrees F. You can use a thermometer or check the temperature by putting a drop of batter into the oil. The batter should not turn brown right away. Instead, it should rise immediately to the surface and turn a very light golden brown.
To make the batter, mix together all the dry ingredients––the flour, baking powder, cornstarch, salt, turmeric, and white pepper. When you’re ready to fry, mix in the sesame oil and cold seltzer water until the batter is smooth.
Next, drop the fish fillets into the batter. Ensure they are evenly coated, but allow the excess to drip off (if there’s too much batter on the fish, you’ll end up with dough balls!). Carefully place the fish into the oil one piece at a time, ensuring that they don’t stick to each other. Fry in batches so that the fish pieces aren’t overcrowded, frying for 3-4 minutes or until golden brown.
Scoop the fried fish out and transfer to a cooling rack placed over a baking sheet to drain. Repeat until all the fish has been fried.
Next, put two teaspoons of the frying oil in a separate wok or skillet over high heat, and toss in the onions, and peppers. Stir-fry for 30 seconds, and then stir in the ketchup. Fry for another 20 seconds––frying the ketchup brings out the color and makes for a better depth of flavor in the sweet and sour sauce.
Mix in the pineapple, pineapple juice, red wine vinegar, water, salt, and sugar, and bring the liquid to a low simmer for 2 minutes. With the sweet and sour sauce still simmering, slowly stir in the cornstarch slurry until the sauce is thick enough to coat a spoon.
At this point, if the fried fish fillets have softened, you can refry them in the oil heated to 400F for 30 seconds in larger batches. The higher heat is needed because the oil will cool immediately after putting in a larger batch of fish in the oil。