Preheat the oven to 350F.
In the large bow of an electric mixer,
beat the butter until it is very creamy.
Add the confectioners' sugar and beat well,
about 5 minutes. Beat in the vanilla.
Sift the flours with the baking powder and salt,
then add them to the butter mixture,
beating only until well combined.

With floured fingers, gently pat the dough into
two ungreased 8" round cake pans.
Using the floured tines of a fork, score the shortbreads into eighths.
Press the tines around the edges of each shortbread
to resemble fluting, and prick the shortbread
with a decorative design, if desired.

Bake for 20-25 minute, or until the edge of
the shortbread is just beginning to brown.
Allow to cool 10 minutes on a rack.
While the shortbread is still warm,
gently cut through the marked-off wedges.
Using a pointed metal spatula or pie server,
carefully lever out the shortbread wedges
and allow them to cool completely on a rack.
Make 16 wedge-shaped cookies.