Scrub the 4 medium potatoes well, then cut into ¼" thick batons. Dry thoroughly with paper towels and leave them sitting on paper towels to allow the surface of the potatoes to dry out for about 30 minutes. You can skip this step if you're pressed for time, but your potatoes won't turn out as crisp.
4 medium potatoes
Mix the ⅔ cup all-purpose flour, 2 tablespoons cornstarch, ¼ teaspoon paprika, and ¼ teaspoon onion powder in a medium bowl until well combined. Dust the 4 medium fish fillets with the flour mixture on all sides.
⅔ cup all-purpose flour, 2 tablespoons cornstarch, ¼ teaspoon paprika, ¼ teaspoon onion powder
Add 1 ½" of vegetable oil to a heavy bottomed pot and heat to 330 degrees F. Line a 2 wire racks with 2 layers of paper towels each.
vegetable oil
Fry the potatoes in batches until a light tan color and the edges are just starting to brown. Transfer the fried chips to one prepared rack to drain.
When the potatoes are done frying, add the ¼ teaspoon baking powder to the flour mixture and whisk together. Then add the cold ½ cup beer to the flour mixture and lightly whisk together. It's okay if there are still a few lumps, just make sure you do not overmix the batter or it will end up heavy.
¼ teaspoon baking powder, ½ cup beer
Dip the fillets in the batter and fry them in batches. Flip the fillets over with tongs when you see the edges start to turn light brown. Transfer to the second prepared rack as they finish frying.
4 medium fish fillets
When the fish is done frying, increase the heat of the oil to 375 degrees F. Fry the chips a second time until they are golden brown and crisp. Drain on a rack and sprinkle with Salt.
Salt
Fry the fish a second time at the higher temperature until golden brown. Drain on a rack. Serve the fish and chips with Lemon wedges or vinegar.
Lemon wedges