Prep the potatoes: Peel and cut the potatoes into thick fries. Soak in cold water with vinegar for 30 minutes (removes starch and makes them crispier).
Dry the fish: Pat the fillets dry with paper towels. Season lightly with salt and pepper.
Make the batter: In a bowl, mix 1 cup flour, baking powder, garlic powder, and paprika. Slowly whisk in the cold beer until smooth.
Heat the oil: In a large heavy pot or deep fryer, heat oil to 350°F (175°C).
Fry the chips (first round): Drain and dry the potatoes. Fry in batches for 3–4 minutes until pale and soft. Remove and let them rest.
Fry the fish: Lightly dredge each fillet in the extra flour, then dip into the batter. Carefully lower into the hot oil. Fry for 6–8 minutes until golden and crisp. Remove to a wire rack or paper towels.
Finish the chips: Fry the chips again for 2–3 minutes until crispy and golden. Drain and season with salt.
Serve immediately with lemon wedges, tartar sauce, and a sprinkle of parsley.