Preheat oven to 325°F (165°C)
In a large mixing bowl, cream the softened butter and powdered sugar together until smooth and creamy
Sift in the cornstarch and flour, then gently mix until a soft dough forms. Avoid overmixing to keep the shortbread tender
Press the dough evenly into an ungreased baking pan or roll it out and cut into shapes
Prick the surface with a fork to prevent puffing
Bake for 20–25 minutes or until the edges are just lightly golden
Remove from oven and allow to cool in the pan for 5 minutes before transferring to a wire rack to cool completely
