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 evenly with salt and black pepper.
03 - Set up three shallow bowls: first with flour, second with beaten eggs, third with panko and cornmeal mixed together.
04 - Dredge each fish piece in flour, shaking off excess. Dip into egg mixture, then press firmly into panko mixture to coat thoroughly on all sides.
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 and bake 10–12 minutes, flipping halfway through.
06 - Combine mayonnaise, chopped pickles, capers, lemon juice, Dijon mustard, and parsley in a small bowl. Mix thoroughly and refrigerate until serving.
07 - Lightly toast slider bun halves in oven or toaster until golden brown, about 2–3 minutes.
08 - Place cooked fish fillet on bottom bun. Top with cheese slice (allow residual heat to melt slightly), lettuce leaf, and generous tablespoon of tartar sauce. Cover with bun top and serve immediately.