Preheat the oven to 160°C (320°F) and line a baking sheet with parchment paper.

Cream the butter and sugar together until light and fluffy.

Sift the flour, cornstarch, and salt together, then gradually mix into the butter mixture to form a soft dough.

Roll the dough out on a lightly floured surface to about 1 cm thickness.

Use a cookie cutter or shape the dough into a rectangle and slice into traditional shortbread fingers.

Place the shaped dough onto the prepared baking sheet. Prick the surface with a fork for a classic shortbread design.

Chill in the refrigerator for 10 minutes to help maintain the shape during baking.

Bake for 20-25 minutes until pale golden. Avoid over-browning to maintain the soft, crumbly texture.

Allow the shortbread to cool completely before serving.