01 - Preheat oven to 400°F or heat oil in a large skillet for shallow frying.
02 - Season fish pieces with salt and pepper on all sides.
03 - Prepare three shallow bowls: one with flour, one with beaten eggs, and one with mixed panko and cornmeal.
04 - Dredge each fish piece in flour, dip in egg, and coat thoroughly in panko-cornmeal mixture.
05 - Fry fish in batches for 2–3 minutes per side until golden and cooked through, or bake on a lined tray for 10–12 minutes, turning once.
06 - Mix mayonnaise, pickles, capers, lemon juice, Dijon mustard, and parsley in a bowl; chill until needed.
07 - Lightly toast slider buns for added texture.
08 - Place fish fillet on bottom bun half. Top with cheese slice, lettuce, and generous spoonful of tartar sauce. Cover with top bun and serve immediately.