Whisk both flours together in a bowl and set aside.
Cream together the butter, sugar, salt, and vanilla on medium speed for a few minutes until light and fluffy. Remove the bowl from the mixer and stir in the flours by hand with a wooden spoon.
Turn out the dough onto a clean surface. Use your hands to make a large solid ball out of the dough. Flatten the dough and shape it into a ¾ inch thick rectangle.
Double wrap the dough in plastic and refrigerate for at least 2 hours or overnight. I prefer to keep it overnight in the refrigerator to firm up.
The next day, line cookie sheets with parchment paper or pre-grease them with baking spray.
Preheat the oven to 325 F degrees.
On a lightly floured surface of your counter, place the dough and dust the top of it a little flour. With a lightly floured rolling pin, gently roll the dough to ¼ inch thick for thin cookies or ¾ inch thick for bars.
Using a round cookie cutter, cut the dough into 2-inch diameter circles. (Or cut cookies in squares or rectangles if preferred). Place the cookies on baking sheets at 1 inch apart. Prick the centers with a fork. Make an even number of cookies if you plan to pair them as a jam-filled cookie.
Sprinkle the top with some granulated sugar. Bake at 325 F degrees for 15 to 17 minutes or till the edges are light gold in color. Cool cookies on wire racks for at least 30 minutes.
For the homemade mango jam, here's my recipe from a past blog post. To fill cookies: Spread half a teaspoon of jam on one side of a cookie. Cover jam-filled side with another cookie. Store in air tight containers. These cookies can be stored in plastic freezer bags, and if frozen will keep for two to three weeks.
Cook's comments : In the original recipe, the author suggested use all-purpose flour if you can't find rice flour. I substituted all purpose for rice flour in this recipe and the results were just as good.