Instructions:
- Prepare the Tartar Sauce: Combine mayonnaise, chopped pickles, dill, capers, lemon juice, and Dijon mustard in a small bowl. Mix well, cover, and refrigerate.
- Prepare the Fish & Dredge Station: Pat fish fillets completely dry. Lightly season. Set up three shallow dishes: 1) Plain flour, 2) Whisked eggs, 3) The batter mix (prepared in the next step). Dust fish in flour, dip in egg, then coat fully in batter. Set aside.
- Prepare the Beer Batter: In a bowl, vigorously whisk together the 1 cup flour, cornstarch, baking powder, salt, and pepper. Pour the ice-cold beer in and whisk just until streaks disappear (a few lumps are fine). Place in the fridge for 30 minutes to chill thoroughly.
- Frying Setup: Pour oil into a deep pot to at least 2 inches depth. Heat oil to exactly 365°F (185°C) using a thermometer. This temperature control is essential for crispy fish.
- Fry the Fish: Carefully lower 1 or 2 battered fillets into the hot oil without overcrowding. Fry for 4–6 minutes per side until deep golden brown and shatteringly crisp. Remove fish and place on a wire rack over a baking sheet; sprinkle immediately with fine sea salt.
- Repeat Frying: Ensure the oil returns to 365°F (185°C) between batches before frying the next set of fillets.
- Assembly: Lightly butter the split buns and toast them until golden brown. Spread tartar sauce generously on both halves. Layer lettuce on the bottom bun, top with the hot, crispy fish, and add sliced pickles. Place the top bun on and serve immediately.