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 both sides generously with salt and black pepper.
03 - Set up 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 wash, allowing excess to drip off, then press firmly into panko-cornmeal mixture to coat completely.
05 - For frying: cook fish in batches for 2-3 minutes per side until golden brown and fish flakes easily. For baking: arrange on parchment-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 small bowl. Mix thoroughly and refrigerate until assembly.
07 - Lightly toast slider bun halves in a dry skillet or under the broiler for 1-2 minutes until golden.
08 - Place cooked fish fillet on bottom bun half. Top with cheese slice, lettuce, and generous tablespoon of tartar sauce. Cover with top bun and serve immediately.