Alison,This recipe is taken from "The New York Times" cookbook.

Scotch Shortbread:
Yield:16-20 wedges

1/4 lb.plus 3 Tbls.butter, at room temperature
1/2 c.confectioners sugar
1&1/2 c.plus 2 Tbls.flour
Pinch of salt

1.Preheat the oven to 325 degrees F.
2.Cream the butter,add the sugar gradually & beat till fluffy.If desired,use an electric mixer at medium speed.
3.Sift the flour & salt into the creamed mixture &
blend thoroughly with the hands.
4.Press the mixture into a 9"pie plate & pinch the edge to form a fluted rim.Prick the surface with a fork.Mark into 16-20 wedges,cutting about half-way thru the dough.
5.Bake till firm when pressed gently in the center or about 50 minutes,the shortbread should not be brown.In an aluminum pan bake on the lower rack,in a glass pan bake on the center rack.
6.Cool the shortbread in the pan.To serve,place right side up on a cutting board & cut in wedges where marked.