Beat together butter and sugar with an electric mixer at
medium speed until pale and fluffy. At low speed, mix in flour mixture
until well blended.
Divide dough in half and pat into 2 (8-inch) round
ungreased cake pans. Score each round into 16 pieces. Prick all over
with a fork.
Bake until golden, about 1 hour. Run a knife around edges
of pan to loosen shortbread, then cut each shortbread, then cool
completely in pans on racks. When cool, carefully remove with a small
off set metal spatula.
Shortbread keeps in an airtight container at room temperature 1 week.