Amy Voigt’s
1 c soft butter
cream with 5/8 c sugar (this is 1/2c + 2 tbsp)
mix in 2 1/2 c sifted flour

chill then pat to 1/2 ” thick, cut into shapes
bake @ 300 on ungreased sheet for 20-25 min

Grandmother Chisholm’s
cream 1 lb butter cut in 6 c flour, 1/2c rice flour and 1 c sugar
Pat into round shape, bake 30 min at 325  or 45 min at 300

My version:  The Edinburgh Book of Plain Cookery Recipes
1-1/2 cup flour
1/2 cup rice flour
8 ounces butter
1/2 cup sugar

Combine all ingredients in the bowl of a standing mixer, paddle until the dough clumps together, press in to 1 or 2 cake pans (I like 1 for thicker shortbread, Stepahnie uses 2 8-inch pans).  Prick with a fork to decorate if you wish.  Bake in a 350 degree oven for 25 to 35 minutes, or until cooked through and lightly browned.  Cut into appropriate sized pieces while it’s still warm, and allow to cool completely before removing it from the pans.