To deep fry the fish, fill a pot or wok with 2 cups of vegetable oil and bring to medium heat. To test if oil is hot enough, place a wooden chopstick and look for bubbles to form at the end. Carefully add coated fish filet into hot oil, half a batch at a time. Fry until golden brown, 6-8 minutes in total, flipping over halfway. Transfer fried fish to cooling rack to allow excess oil to drip.