Pat the fish fillets dry with paper towels. If they are thick, cut each fillet into two sandwich-sized pieces (you should have about 4 pieces total). Season both sides lightly with 1/2 tsp salt and 1/2 tsp black pepper.

Set up breading station

Place the flour in a shallow dish. In a second shallow dish, whisk together the eggs and milk until smooth. In a third dish combine the breadcrumbs, paprika, garlic powder, remaining 1/2 tsp salt, and remaining 1/2 tsp black pepper.

Bread the fillets

Working one piece at a time: dredge a fillet in flour, shaking off excess; dip into the egg mixture, letting excess drip; press firmly into the breadcrumbs to coat evenly. Place breaded fillets on a plate and repeat with remaining pieces.

Pan-fry the fish

Heat a large skillet over medium-high heat and add 3 tablespoons vegetable oil. When oil is hot and shimmering (but not smoking), add fillets in a single layer without crowding. Cook 3-4 minutes per side, or until golden brown and cooked through (internal temperature 145°F / 63°C) — thickness will affect time. If using cheese slices, place one cheese slice on each fillet during the last 30 seconds of cooking and cover briefly to melt. Transfer cooked fillets to a paper-towel-lined plate.

Sauce

Make the sauce by combining mayonnaise, lemon juice, Dijon mustard, minced capers (if using), minced dill or parsley, 1 tsp salt, and 1/2 tsp black pepper in a small bowl. Taste and adjust seasoning or lemon to preference. Chill until ready to assemble.

Sandwich & Toppings

Prepare buns and vegetables

Slice buns and lightly toast them in a dry skillet or under a broiler for 1-2 minutes until lightly golden. Thinly slice the tomato and rinse/shred the lettuce. Have pickle slices ready.

Assemble sandwiches

Spread about 2 tablespoons of the sauce on the bottom half of each bun. Place a piece of cooked fish on top, then add 1/2 cup shredded lettuce, 2-3 tomato slices, and 2 pickle slices. Spread a little sauce on the top bun and close the sandwich. Serve immediately while fish is hot.

Serving suggestion

Serve with extra sauce on the side, lemon wedges, and a side of fries or a simple green salad.