Step 1: Prepare the Fish

Start by patting the fish fillets dry with paper towels. This step is crucial because excess moisture can prevent the batter from adhering properly. Lightly season the fillets with a pinch of salt and pepper to enhance their natural flavor.

Step 2: Mix the Batter

In a mixing bowl, whisk together the flour, cornstarch, baking powder, salt, black pepper, and garlic powder (if using). Gradually add the cold sparkling water or beer while whisking continuously. Be careful not to overmix—the batter should be smooth but still slightly lumpy. Overmixing can result in a dense coating instead of a light, crispy one.

Step 3: Heat the Oil

Pour vegetable oil into a deep skillet or deep fryer and heat it to 350°F (175°C). The oil should be hot enough to fry the fish evenly but not so hot that it burns the batter before the fish cooks through. To test the oil, drop a small amount of batter into the pan—if it sizzles and rises to the surface immediately, the oil is ready.

Step 4: Coat the Fish

Lightly dredge each fish fillet in flour before dipping it into the batter. This extra layer of flour helps the batter stick better to the fish. Allow any excess batter to drip off before carefully placing the fillet into the hot oil.

Step 5: Fry the Fish

Fry the fish in small batches to avoid overcrowding the pan. Cooking too many pieces at once will lower the oil temperature and result in soggy, greasy fish. Each fillet should be fried for 3–5 minutes per side, or until it turns golden brown and crispy.

Use a slotted spoon or tongs to remove the fish from the oil and transfer it to a paper towel-lined plate to drain excess oil. Repeat the process with the remaining fillets.