Here is my authentic Scottish Shortbread recipe which came from Margaret McLaren, a Scottish friend from when I lived near Atlanta back in 1967.
3 sticks butter (I use Challenge unsalted)room temp.
1 heaping cup powdered (icing) sugar
1 egg yolk
4 cups ap flour
Preheat oven to 300*, cut wax paper circles to fit 8"-9" cake pans. I wonder whether parchment would work?
Sift the sugar into a large bowl and knead in the butter. Add the egg yolk and mix in well. Add the flour one cup at a time. Roll into a lump the size of a jelly roll, cut into 3. Pat onto the wax paper to fit the pans. Prick all over with a fork and crimp the edges, and cut almost through in wedges. Bake 45 minutes to 1 hour - mine didn't take that long. The shortbread should be pale in color. Cool on rack, careful, I managed to crack all of mine!
I also forgot that I wanted to add some rice flour because I had read that it gave a nice crunch. Oh well, next year. Merry Christmas from Whidbey Island, A.