Hi
I did a little research to see what I could find for you.
Here is the only one I could find that listed Brown Sugar in the recipe at least out of those I went through. It is also cut in wedges or triangles it was from a newspaper So maybe it is the same and one paper got it from another ;0)
April

The Star'S Scottish Shortbread

1 cup butter; softened
1 2/3 cup flour; all purpose
1/3 cup rice flour
1/4 cup sugar, granulated
1/4 cup brown sugar; packed

Grease 8-inch round cake pan. Line bottom with wax paper.

In bowl, cream butter until fluffy. Mix in all purpose and rice flours, and white and brown sugar with electric beater until dough is crumbly but clumps together when pressed. Pat evenly into prepared pan.

Bake in preheated 352F oven 45 minutes.

Remove from oven briefly, with sharp knife, score into 12 wedges, cutting about halfway through dough. Price decoratively with fork.

Return to oven; bake about 15 minutes longer or until just lightly browned at edges. Cool in pan on rack 30 minutes. Loosen sides;invert again on cooling rack so cookie is right side up. Cool completely. MAKES: 12 large wedges