Meanwhile, make the glaze: In a small bowl, whisk together the confectioner’ sugar, whisky, and salt until smooth. Dip the tops of the cookies into the glaze, shaking off any excess. Place a piece of candied ginger in the center of each cookie, using a little more glaze to adhere it if necessary. Set aside at room temperature until the glaze has set, about 30 minutes, before serving. Cookies will keep in an airtight container at room temperature for at least 5 days.