Combine first 6 ingredients in a large bowl. Combine the vanilla and next 2 ingredients, and add to the flour mixture, stirring until well-blended (dough will be dry).
Turn the dough out onto a lightly floured surface, and knead lightly 7 or 8 times. Shape dough into a 16-inch-long roll. Place roll on a baking sheet coated with cooking spray, and flatten roll to 1-inch thickness.
Bake at 350° for 30 minutes. Remove roll from baking sheet to a wire rack, and let cool 10 minutes.
Cut roll diagonally into 24 (1/2-inch) slices, and place slices, cut sides down, on baking sheet. Reduce oven temperature to 325°, and bake for 10 minutes. Turn the cookies over, and bake for an additional 10 minutes (the cookies will be slightly soft in center but will harden as they cool). Remove from baking sheet, and let cool completely on wire rack.