The batter can be made several hours in advance and refrigerated until ready to use.
1. To make the batter: Combine the flour, cornstarch, beer, egg, and salt in a large mixing bowl and whisk well. The batter will be very light-slightly thinner than a regular pancake batter. Cover and refrigerate for at least 20 minutes, or up to 3 hours.
2. Line a baking sheet with paper towels. Heat 3 inches of oil to 375 F in a 4-to-5-quart Dutch oven over medium heat or in a deep fryer.
3. While the oil is heating, dry the fish fillets between several thicknesses of paper towels. Season with the spiced salt (or salt and pepper). Drop the fillets into the batter and toss with tongs to coat evenly.
4. When the oil is hot, lift the fillets one by one from the batter with the tongs, letting excess batter drip back into the bowl, and lower them into the oil, holding each fillet suspended in the oil for a few seconds to set the batter and prevent it from sticking to the bottom of the pot. The temperature of the oil will drop when the fish is added, but you overheated the oil, to 375 F, to compensate for this. Don't let the oil come back over 350 F once it recovers. Fry the fillets until deep golden brown, about 5 minutes. Transfer them to the paper towel-lined baking sheet with tongs. Serve the fish hot with the French Fries, coleslaw, tartar sauce, lemon wedges, and malt vinegar.
For the tarter sauce:
1. Combine the mayonnaise, lemon juice, onion, parsley, pickles, capers, and eggs in a large bowl and whisk well to combine. Transfer to a bowl or another container; cover tightly, and refrigerate until ready to use. Tartar sauce keeps refrigerated for up to one week.
Serve with Boardwalk French Fries for a great summer meal.