In a large mixing bowl, beat butter with an electric mixer until smooth. Beat in brown sugar, granulated sugar, pumpkin pie spice, vanilla, baking powder and salt. Beat in egg until well combined. Beat in as much flour as possible with mixer. Stir in remaining flour with a spoon. If necessary, chill dough for easier handling.
Preheat oven to 375°F. On a lightly floured surface, roll out dough to ¼-inch thickness, adding more flour as necessary. Use 4-to-6-inch snowflake cutters to cut cookie shapes. Place 1 inch apart on ungreased cookie sheet. Bake for 6 to 8 minutes or until edges just begin to brown. Cool cookies on wire racks.
