Pour vegetable oil into a wide, heavy pot or fryer until it is deep enough to submerge the fish halfway. Heat to 350–375°F (175–190°C). Keep a thermometer on hand and maintain temperature as you fry.

Mix dry coating

In a shallow bowl, whisk together All-purpose flour, cornstarch, baking powder, paprika, garlic powder, onion powder, salt, and black pepper until well combined.

Prepare wet batter

In a second bowl, whisk eggs. Stir in cold beer or sparkling water to form a smooth, slightly thick batter. The beer helps with lightness.

Set up dredging station

Place beaten eggs (for dipping after flour) and breadcrumbs in separate shallow dishes. Arrange the fish fillets in a tray ready for coating.

Dredge and coat fillets

Pat dry the fish fillets. Dredge each fillet in the seasoned flour, shake off excess. Dip into the beer batter, allow excess to drip back, then coat with breadcrumbs for a crunchy crust.

Fry the fish

Carefully lower coated fillets into hot oil, in batches to avoid crowding. Fry 3–4 minutes per side until golden and crispy and the internal temperature reaches 145°F (63°C). Remove with a slotted spoon and drain on a rack or paper towels.

Serve

Transfer the fried fillets to plates and serve with unsweetened apple sauce on the side and lemon wedges for squeezing over.