1. Heat the oven to 325 degrees F. Line a cookie sheet with (unbleached) parchment paper or a silicone baking liner.

2. In an electric mixer on low speed, beat the sugar with the butter until smooth (about 1 minute). Add the flours. Beat on medium-low speed until the dough comes together. If it doesn't come together in the mixer after a minute or two, turn the mixer off and use your hands to form a cohesive dough.

3. Pinch off small pieces of dough (about the size of a teaspoon) and use your hands to roll them into small balls (you should have 10 balls of approximately the same size when you are done rolling them). Arrange cookies on the prepared cookie sheet 1 1/2 to 2 inches apart. Using your thumb, press down into the middle of each ball to make a well. (You want the indentation to be deep enough to hold the filling, but you don't want to press all the way through the dough.) If the edges of the cookies crack as you press the centers down, gently pinch/press them back together.

4. Bake until the tops of the cookies look dry, and they're beginning to brown, 16-18 minutes. Let the cookies sit for 5 minutes and then transfer them to a wire rack to cool completely (while they are cooling and still a bit soft, you can press the indentations down a bit more, if necessary). Serve immediately, or cover and store at room temperature for up to 2 days. Just before serving, fill each cookie's indentation with the filling(s) of your choice.