01 - Preheat oven to 400°F or pour enough oil in a large skillet for shallow frying over medium-high heat.
02 - Pat fish pieces dry with paper towels, then season both sides generously with salt and pepper.
03 - Arrange 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 wash, allowing excess to drip off. Press firmly into panko mixture, coating completely.
05 - For frying: cook in batches 2–3 minutes per side until golden brown and fish flakes easily. For baking: arrange on parchment-lined baking sheet, bake 10–12 minutes, turning halfway through.
06 - Combine mayonnaise, chopped pickles, capers, lemon juice, Dijon mustard, and parsley in a small bowl. Mix thoroughly and refrigerate until ready to serve.
07 - Lightly toast slider buns cut-side up until golden and warm, about 2–3 minutes.
08 - Place cooked fish fillet on bottom bun. Top with cheese slice (it will melt from residual heat), add lettuce, and spread with tartar sauce. Cover with bun top and serve immediately.