Preheat the oven to 325°F. Cream the butter and sugar well until the texture becomes light and fluffy, five to seven minutes.
Add 3-¾ cups flour to the butter mixture. Mix well to form a dough. Turn the dough onto a floured surface and knead for five minutes. Add the remaining flour as needed to form a soft dough. Editor's Tip: Don't add too much extra flour to the dough. This is one of the most common shortbread mistakes.
Place the dough on a sheet of baking parchment, then roll it out to a 16x9-inch rectangle. Transfer the slab of dough to a baking sheet and cut it into 3x1-inch strips. Prick each cookie several times with a fork. Place the tray in the fridge for 30 minutes or overnight.
Arrange the cookies 1 inch apart on an ungreased baking sheet. Bake for 20 to 25 minutes, until the cookies are lightly browned. Remove from the oven and transfer to wire racks to cool.
