Position an oven rack in the center of the oven.
In a blender or food processor, process the cashews until finely ground.
In a medium bowl, combine all the dry ingredients except the sugars. Stir with a whisk to blend.
In a stand mixer fitted with the paddle attachment, cream the butter, ground cashews, and the sugars on medium speed until light and fluffy. Gradually beat in the dry ingredients until blended. Beat in the eggs, one at a time, until smooth, stopping to scrape down the sides of the bowl. Beat in the vanilla.
Cover and refrigerate for 1 hour. Using a
Remove from the oven and let cool for 5 minutes on the pan on a wire rack. Transfer the cookies to wire racks to cool completely.
Line a small jellyroll pan with parchment paper. Spread the bottom of a cookie with a generous scoop of ice cream and top that with another cookie, bottom-side down, pressing it to make the cookies adhere. Place on the prepared pan. Working quickly, repeat to sandwich all the cookies. Place the sandwiches in the freezer for 1 hour to set.