In a medium bowl, combine the brown sugar and butter; beat with electric mixer until light and creamy. Beat in flour (knead in the last of the flour if the dough is too thick for your mixer); turn out onto a lightly floured surface and roll to 1/4-inch thickness.
Slice or cut out and use a fork to prick the cookies 3 or 4 times.
Arrange the cookies on ungreased baking sheets and bake for 22 to 26 minutes, until lightly browned around the edges.
Notes
Cooking time depends on thickness. Don't let them brown too much, just lightly around the edges.