Gather ingredients
In a large bowl,mix the remaining 5 tablespoons all-purpose flour with 7 tablespoons cornstarch and 1 teaspoon baking powder. Season lightly with a tiny pinch of fine salt and freshly ground black pepper. (set 2 tbsp of flour aside fro later use)
Using a fork to whisk continuously, add 1/3 cup cold dark beer and 1/3 cup cold sparkling water to the flour mixture and continue mixing until you have a thick, smooth batter. Place the batter in the fridge to rest for 30 minutes to 1 hour.
Peel the potatoes. Then cut into a little less than 1/2-inch-thick slices, then slice these into 1/2-inch-wide sticks. Place the chips into a colander and rinse under cold water.
Place the washed chips into a saucepan of water, to cover them. Bring to a gentle boil over high heat, then simmer on low heat for 3 to 4 minutes. Drain the chips, transfer to a plate with paper towel on top, then pat dry with paper towels. Keep in the fridge until needed.
Lay 4 fish filets on a paper towel and pat dry. Season lightly with a little salt.
Place the 2 tablespoons of reserved flour into a shallow bowl. Toss each fish filet in the flour and shake off any excess. Then, dip the flour-coated fish into the batter.
Once the oil is hot, carefully lower each fillet into the hot oil. Fry until the batter is crisp and golden, turning the fillets occasionally with a large slotted spoon, 6 to 8 minutes. Once the fish turned golden brown, remove the fillets from the oil to the paper-towel-lined baking sheet and sprinke with salt.
Cook the chips in batches until golden and crisp, about 5 minutes. Remove from the oil and drain. Transfer to a baking sheet lined with paper towel and season with salt.
Serve and enjoy when the fish and chips are hot.