This is a recipe from my grandmother. It's similar to other shortbread recipes from Canada in that it uses berry sugar (made from strawberries) instead of cane sugar. Berry sugar is very common on grocery store shelves in Canada (at least western Canada) around Christmas, but it seems much rarer in the United States.
4 cups flour
1 1/2 cups berry sugar
1/2 cup white rice flour
1 pound butter (softened at room temperature)
Mix the dry ingredients, then cut the butter into the dry ingredients until the mixture is like coarse crumbs. Then knead with fingers on board until the mixture is not too crumbly (the heat of your hands will melt the butter enough to allow this).
Form into cookies either by rolling into balls are forming dough logs that you cut into circles with a knife. Cook in a 250 degree (F) oven for about 25 minutes. Do not overcook (if the cookies brown, they are overcooked).
For an interesting variation, add dried blueberries to the dough.
You can also form the dough into little logs, and, after cooked and cooled, dip one end into melted semisweet chocolate. Place the dipped cookies on wax paper and put in fridge to harden the chocolate.