Working with 1 cutlet at a time, place it on a clean work surface, cover with plastic wrap, and pound flat with a flat surface (not a pointed meat tenderizer). The back of a small frying pan works well if you don’t have a flat meat pounder. Repeat with remaining cutlets. Lay them flat and sprinkle with half of the salt and pepper, turn them over and sprinkle with the remaining half on the second side.
Put the breadcrumbs on a wide, rimmed plate. Working with 1 cutlet at a time, press into the panko, turn over and press again. The cutlet should be well coated with the crumbs. Repeat with remaining cutlets.
Heat a large frying pan over medium-high heat. Add enough oil to thickly cover the cooking surface. When the oil is shining from heat, add as many cutlet as fit in a single, uncrowded layer. They should sizzle immediately. Cook until golden brown on one side, 2 to 3 minutes. Turn over and cook until golden brown on the second side, another 2 to 3 minutes.
Transfer the cooked cutlets to a layer of paper towels or a cooling rack to drain. Hold in a warm oven, if you like. Repeat with the remaining cutlets.
Serve hot, warm or even room temperature.