Preheat oven to 325°. Cream butter and brown sugar until light and fluffy, 5-7 minutes. Add 3-3/4 cups flour; mix well. Turn dough onto a floured surface; knead for 5 minutes, adding enough remaining flour to form a soft dough. , Roll to 1/2-in. thickness. Cut into 3x1-in. strips. Place 1 in. apart on ungreased baking sheets. Prick with fork. Bake until cookies are lightly browned, 20-25 minutes. Cool.