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 - Arrange three shallow bowls: first with flour, second with beaten eggs, third with panko breadcrumbs mixed with cornmeal.
04 - Coat each fish piece in flour, shaking off excess. Dip into egg mixture, allowing excess to drip off. Press firmly into panko-cornmeal mixture, ensuring complete coverage.
05 - For frying: cook fish in batches 2-3 minutes per side until golden brown and internal temperature reaches 145°F. For baking: arrange on parchment-lined baking sheet, bake 10-12 minutes, turning once halfway through.
06 - Combine mayonnaise, chopped pickles, capers, lemon juice, Dijon mustard, and parsley in small bowl. Mix thoroughly and refrigerate until assembly.
07 - Lightly toast slider bun halves in oven or skillet until golden brown, approximately 2 minutes.
08 - Place fried fish fillet on bottom bun half. Top with cheese slice (allow residual heat to melt), lettuce leaf, and tablespoon of tartar sauce. Crown with top bun and serve immediately.