01 - Preheat oven to 400°F or heat 1/2 inch oil in a large skillet over medium-high heat for shallow frying.
02 - Pat fish pieces dry with paper towels, then season evenly with salt and black pepper on both sides.
03 - Prepare three shallow bowls: place flour in the first, beaten eggs in the second, and mix panko breadcrumbs with cornmeal in the third.
04 - Dredge each fish piece in flour, shaking off excess. Dip into egg mixture, allowing excess to drip off, then press firmly into panko-cornmeal mixture to coat thoroughly.
05 - For frying: cook fish in batches for 2-3 minutes per side until golden brown and fish flakes easily. For baking: arrange on lined baking sheet and bake 10-12 minutes, turning once halfway through.
06 - Combine mayonnaise, chopped pickles, capers, lemon juice, Dijon mustard, and fresh parsley in a mixing bowl. Refrigerate until ready to assemble.
07 - Lightly toast slider bun halves in the oven or a dry skillet for 1-2 minutes until golden.
08 - Place cooked fish fillet on bottom bun, top with cheese slice, lettuce, and generous spoonful of tartar sauce. Cover with top bun and serve immediately.