Line a 9-inch square metal pan or a 7x11 inch pan with nonstick foil or parchment paper.
Combine the all-purpose flour, rice flour, sugar and ginger (if using) in a large mixing bowl.
Gently melt the butter in a microwave- safe glass measuring cup using 50% power. Try to melt it so that the solids do not separate. That is, once it is very soft and squishy or partially melted, just take it out and stir it.
Mix the vanilla with the melted butter and let it cool for about five minutes.
Add the butter to the flour mixture and stir with a wooden spoon or heavy duty scraper until blended. Transfer mixture to the pan and pat it down flat. Put it in the refrigerator for 30 minutes or until cold.
Preheat oven to 350ºF.
Sprinkle top of shortbread with sugar. Place in the oven and bake for about 30 minutes or until middle appears set and edges are lightly browned.
Using a fork, poke holes in the warm shortbread. Poke them at intervals and plan on cutting around them.
Using a razor blade or sharp knife, score the shortbread gently into 32 fingers (or whatever size you want). Do not lift it from the pan at this point.
Let sit until completely cool, then lift from pan. Use a knife to cut through the areas you lightly scored.
Store in a tin. These stay fresh for weeks.
Notes
Salt: The shortbread gets its salt from the salted butter, but feel free to add an extra pinch if you like sweet & salty. If you are using unsalted butter, add ¾ teaspoon of salt to the recipe.If you have an old coffee grinder or spice grinder, make your own rice flour by grinding 2 ounces of white riceFor best results, weigh your ingredients.Don't over-bake. Edges should be just browned and shortbread should still be pretty soft when you pull it from the oven.NYT (Version Two) 8-Inch Square Pan: Use 240 grams flour, 36 grams (¼ cup) rice flour, 63 grams sugar (5 tablespoons), 228 grams unsalted butter, ½ teaspoon of salt plus a pinch and use an 8 inch square pan rather than a 9 inch square pan. Bake at 350 for about 40 minutes. You can also make the NYT version with salted butter, but add a pinch of extra salt anyway.