Preheat oven to 350°. Cream butter and 1 cup confectioners' sugar until light and fluffy, 5-7 minutes; beat in vanilla. Gradually beat in flour. Stir in pecans. , Shape tablespoons of dough into 2-in. crescents. Place 2 in. apart on ungreased baking sheets., Bake until light brown, 12-15 minutes. Roll cookies in additional confectioners' sugar while warm; cool on wire racks.