Put oven racks in upper and lower thirds of oven and preheat oven to 425oF. Butter 2 large shallow (1 inch deep) baking pans.

Gently pound chicken between sheets of wax paper with flat side of a meat pounder or with a rolling pin until 1/3 inch thick. Cut chicken lengthwise into ½-inch-wide strips.

Stir together butter, salt, and pepper in a shallow dish. Put cornflakes in another shallow dish. Working with 1 strip at a time, dip in butter, then dredge in cornflakes, pressing flakes firmly to help adhere. Transfer as coated to baking pans.

Bake, switching positions of pans halfway through baking, until chicken is golden and cooked through, about 15 minutes total.

Cool chicken pans on racks to room temperature (crust will firm up as it cools).