Pat the fish fillets dry with paper towels. Trim any thin edges so they cook evenly. Lightly season both sides with 1/2 teaspoon salt and 1/4 teaspoon black pepper.

Make batter

In a large mixing bowl, whisk together 1.5 cups all-purpose flour, 1/4 cup cornstarch, 1 teaspoon baking powder, 1 teaspoon salt, and 1/2 teaspoon freshly ground black pepper until well combined.

Add Guinness

Slowly pour 12 fl oz cold Guinness into the dry ingredients while whisking to make a smooth batter. Add 4 ice cubes and continue whisking briefly — the batter should be thick enough to coat the back of a spoon but still fluid. Chill the batter in the refrigerator while you prepare the chips (about 10–15 minutes).

Dust fish

Place 1/2 cup extra flour on a plate. Lightly coat each seasoned fish fillet in the flour, shaking off excess. This helps the batter adhere.

Fry fish

Heat oil in a deep fryer or a heavy, deep pot to 350°F (175°C). Working in batches if necessary, dip floured fillets into the Guinness batter, letting excess drip off, then carefully lower into hot oil. Fry for 5–7 minutes, turning gently once, until the batter is deep golden brown and the fish reaches an internal temperature of 145°F (63°C) and flakes easily. Remove with a slotted spoon and drain on a rack or paper towel-lined sheet. Keep warm in a low oven (200°F / 95°C) while frying remaining fish.

Chips (Fries)

Prepare potatoes

Peel potatoes if you prefer (skin on is fine). Cut into 1/2-inch to 3/4-inch strips for classic chips. Rinse cut potatoes in cold water to remove surface starch until water runs clear.

Soak and dry

Place rinsed potatoes in a bowl of cold water with 1 tablespoon white vinegar (optional) and refrigerate for at least 30 minutes or up to 2 hours to help crispness. Drain and spread on a clean towel; pat completely dry.

First fry (blanch)

Heat oil in a deep fryer or heavy pot to 300°F (150°C). Fry potatoes in batches for 4–6 minutes until softened but not colored. Remove and drain on paper towels.

Second fry (crisp)

Increase oil temperature to 375°F (190°C). Fry the blanched potatoes in batches for 2–3 minutes or until golden and crisp. Transfer to a tray lined with paper towel and immediately season with 1 teaspoon salt, tossing to coat evenly.

Tartar Sauce & Serving

Make tartar sauce

In a small bowl, combine 1/2 cup mayonnaise, 2 tablespoons finely chopped dill pickle, 1 tablespoon chopped capers, 1 tablespoon fresh lemon juice, 1 tablespoon chopped fresh parsley, 1/4 teaspoon salt, and 1/4 teaspoon freshly ground black pepper. Stir until smooth and chill until ready to serve.

Plate and serve

Place a portion of hot chips on each plate. Top with a Guinness-battered fish fillet. Serve immediately with a spoonful of tartar sauce, lemon wedges, and extra malt vinegar or ketchup if desired. Enjoy while hot.