In a bowl, with an electric mixer on medium speed, beat butter, 1/2 cup powdered sugar, and almond extract until smooth. In another bowl, mix flour, baking powder, and salt; stir or beat into butter mixture until well blended. Stir in cashews (if mixture is crumbly, squeeze into a smooth, compact ball).
Divide dough in half; flatten each portion into a 1-inch-thick disk. Wrap each disk airtight and freeze until firm, about 20 minutes. On a lightly floured board, with a floured rolling pin, roll dough, a portion at a time, to 3/16 inch thick.
With a floured 3-inch star-shaped cutter, cut out cookies (if dough becomes too soft to handle, freeze briefly until firm again). With a wide spatula or your fingers, transfer cookies to buttered or cooking parchment-lined 12- by 15-inch baking sheets, spacing them about 1 inch apart. Gather scraps, pat into a ball, and repeat rolling and cutting.
Bake cookies in a 300° oven until golden, 15 to 18 minutes; if baking more than one pan at a time, switch pan positions halfway through baking.
With a wide spatula, transfer cookies to racks to cool. If hot cookies start to break, slide a thin spatula under them to release, let stand on sheets to firm up, about 5 minutes, then transfer to racks to cool completely. Dust cookies with remaining 2 tablespoons powdered sugar.