Pat dry the fish fillets and lightly season with salt. Sprinkle with cornstarch on both sides and make sure that they are completely coated. Set aside.
4 white fish fillets, Kosher salt, 1 tablespoon cornstarch
In a shallow mixing bowl, whisk together the all-purpose flour, cornstarch, garlic powder, salt, and black pepper.
1 cup all-purpose flour, 2 tablespoons cornstarch, ¼ teaspoon garlic powder, ¼ teaspoon kosher salt, ¼ teaspoon ground black pepper
Slowly pour in the cold beer while stirring until you achieve a smooth and thick batter. Afterward, stir in the baking powder and set aside.
1¼ cups cold beer, ½ teaspoon baking powder
In a large skillet, heat enough vegetable oil to submerge the fish fillets. Heat the oil to 350°F (175°C).
Vegetable oil
Coat the fish fillets in the batter and carefully place them into the hot oil.
Fry for approximately 4-5 minutes on each side or until the fish turns golden brown and easily flakes with a fork. Once fried, transfer the fish fillets to a paper towel-lined plate to remove any excess oil.
Lightly toast the brioche buns in the skillet or on a griddle until they are slightly crispy.
4 brioche buns
Spread tartar sauce on the bottom half of each bun and add fresh lettuce. Place a fried fish fillet on top, and generously spoon more of your homemade tartar sauce over the fish.
½ recipe homemade tartar sauce, 4 leaves fresh lettuce
Close the sandwiches and serve immediately, along with your choice of side dishes, such as coleslaw, potato chips, or a simple garden salad.