If your fishmonger didn’t do this part already: Remove the fish’s head, tail and fins, then chop fish into ½-1 inch sections, going straight down through the spine (see photos in post).Optional step: Marinate the sections of fish in 5 slices of ginger and 2 tablespoons Shaoxing wine for an hour before frying.
Heat up 4 cups of oil in a pot or a wok to 375℉/190℃. If you’re not sure about the temperature, test it with a small piece of fish—it should float immediately and bubble energetically. Pat fish pieces dry with a paper towel and add one or two pieces to the oil at a time—if you add more, the oil temperature will drop too much. Also, the fish pieces want to stick to each other, so don’t crowd them.
Fry the fish pieces for 2-3 minutes per side, or until the fish is brown. Not golden brown, brown brown. Try to maintain oil temperature between 350-380℉ (~175-195℃) during this process, but don’t worry too much about it—it’s very forgiving. Err on the side of overcooking, since you want the fish to be almost crunchy.
For jiaoyan fish, add fresh-fried fish pieces to a bowl with a few tablespoons of shaokao spice and toss well to coat evenly. It’s important to do this while fish is still very hot so the spices will stick.For tangcu fish, dunk the fish into the chilled marinade, making sure to coat all surfaces.
Serve jiaoyan fish immediately; serve tangcu fish immediately or after chilling, covered in the marinade, in refrigerator for up to 3 days. Sprinkle the tangcu fish with osmanthus flowers when plating for restauranty flair.