Preheat oven to 325 degrees. Line a baking sheet with parchment paper. Set aside.

In a large bowl, whisk together the flours, sugar, baking soda, salt, and xanthan gum. Using a pastry blender, cut the butter into the dry ingredients until the mixture resembles coarse crumbs. Stir in the chopped pistachios and dried cranberries, then add the eggs, yogurt, and extracts, mixing until the dough comes together. The dough will be very sticky.

Divide the dough in half. Using lightly dampened hands, shape each half of the dough into a 12 x 2 1/2-inch parallelogram on one side of the baking sheet; repeat with the other half of the dough. Leave as much space as possible between the two halves, as the dough will expand and spread in the oven.

Bake for 45 minutes, until golden brown. Remove the biscotti from the oven; lower the oven temperature to 250 degrees. Allow the biscotti to cool for 5-10 minutes, then slice the rectangles into pieces 3/4-inch wide. Place the pieces back on the baking sheet, standing up. Return to the oven and bake for an additional 40 minutes. Without removing the cookies, turn off the oven and allow the cookies to cool on the baking sheet in the oven.

Once cool, cookies can be stored in an airtight container for 2-3 weeks, or frozen for longer.