Pour your frying oil into a deep-sided skillet or heavy pot, ensuring it is at least 2 inches deep. Heat the oil over medium to medium-high heat until it reaches exactly 350°F on a kitchen thermometer.

While the oil heats, arrange your raw fish fillets flat on a heavy layer of paper towels. Press additional paper towels firmly over the top to completely dry the surfaces. Pro Tip: If the fish has any lingering surface moisture, it will turn into steam the moment it hits the hot oil. This trapped steam pushes the batter away from the fish, causing the crust to separate, balloon, and crack open instead of sticking firmly to the protein core.

In a large bowl, whisk together the all-purpose flour, yellow cornmeal, baking soda, baking powder, and salt until completely uniform and free of any lumps.

Pour the ice-cold ginger ale directly into the dry ingredients. Whisk gently and quickly just until the flour disappears and a smooth batter forms. Crucial: Do not over-whisking. The combination of baking soda, baking powder, and carbonated soda creates an intense network of micro-bubbles. Over-mixing will deflate these carbon dioxide pockets, resulting in a dense, heavy, doughy crust rather than the signature light, shattered-glass texture.

Dip a thoroughly dried fish fillet into the batter, turning it over to coat it entirely. Lift the fish up and let any heavy excess batter drip back into the bowl for 3 seconds.

Gently lower the coated fish away from you into the 350°F oil. Fry for 4 to 6 minutes per side. Keep a close eye on the stove heat; if the oil starts smoking, drop the temperature slightly to prevent the cornmeal from scorching.

Once the exterior is a deep, uniform golden brown and the fish flakes easily inside, lift the fillets out using a slotted spoon or spider wire mesh. Transfer them immediately to a paper towel-lined plate to drain off any surface grease. Serve piping hot.