How to Make It
Preheat the oven to 375°. Line 2 large baking sheets and 2 wire racks with parchment paper. In a large bowl, using a handheld electric mixer, beat the butter with 1/2 cup of the confectioners' sugar at medium speed until creamy. Add the vanilla extract. At low speed, beat in the flour, roasted cashews and salt. Scrape the dough onto 4 sheets of plastic wrap and form into 1-inch logs. Wrap the logs and refrigerate until firm, at least 20 minutes.
Cut the logs into 1-inch lengths and roll the lengths into balls. Arrange the balls on the baking sheets about 3/4 inch apart. Bake the cookies in the lower and upper third of the oven for 20 minutes, or until golden and set; shift the baking sheets from top to bottom and front to back halfway through.
Fill a pie plate with about 2 cups of confectioners' sugar. Immediately roll the hot cookies, a few at a time, in the confectioners' sugar to coat; then transfer to the parchment-lined racks to cool completely. Reroll the cooled cookies in the confectioners' sugar and transfer to a plate.
The snowball dough is sweetened with powdery confectioners' sugar rather than granulated sugar. Always sift confectioners' sugar before measuring to remove clumps that can throw off measurements.