Crispy Fish Sandwich

Ingredients

• 1 small red onion, thinly sliced into rounds
• 4 oz. bread-and-butter pickles, plus ½ cup brine
• ¾ cup mayonnaise
• ⅓ cup chopped dill
• 2 tsp. hot sauce
• 1 tsp. freshly ground black pepper
• 2 tsp. fresh lemon juice, plus wedges for serving
• 1 Tbsp. kosher salt, divided
• 2 large eggs, lightly beaten
• 1½ cups panko (Japanese breadcrumbs)
• ½ cup all-purpose flour
• 2 flounder fillets (about ⅔ lb. total), cut in half crosswise on a diagonal
• ⅔ cup vegetable oil
• 3 cups shredded iceberg lettuce
• 8 slices Pullman bread
• 1 cup potato chips, plus more for serving

Steps

1. Combine onion, pickles, and pickle brine in a small bowl.
2. Mix mayonnaise, dill, hot sauce, pepper, 2 tsp. lemon juice, and ½ tsp. salt in another small bowl.
3. Place eggs, panko, and flour in 3 separate shallow medium bowls. Season each fish fillet with ½ tsp. salt. Working one at a time, dredge fish in flour, shaking off excess. Coat evenly with egg, allowing excess to drip back into bowl. Coat with panko, pressing to adhere. Transfer fish to a plate.
4. Heat oil in a large skillet over medium. Cook fish until breading is golden brown and cooked through, 2–3 minutes per side. Transfer fish to a paper towel-lined plate. Season fillets with ½ tsp. salt total.
5. Spread 1 heaping Tbsp. mayonnaise mixture on one side of each slice of bread. Pile each bottom slice with ¾ cup lettuce, 1 fish fillet, a small handful of potato chips, and ¼ cup onion mixture. Close sandwich with second slice of bread, mayo side down, and push down lightly to crush potato chips. Transfer to a platter. Repeat with remaining sandwiches. Serve with lemon wedges and more potato chips alongside.
6. Do Ahead: Pickled onions and dill sauce can be made 1 day ahead. Cover and chill.