Preheat oven to 350 degrees.
Line a 9x13 baking dish with foil, leaving an overhang on all sides and spray with non-stick spray.
In a medium bowl, add flour, pie spice, cinnamon, baking soda, and salt and whisk, then set aside.
Using an electric mixer, cream butter and sugar on medium-high speed until smooth.
Beat in egg and maple syrup until combined.
Add in pumpkin puree and mix until well incorporated.
Reduce speed to low, and mix in dry ingredients until just combined.
Fold in white chocolate chips.
Spread batter evenly in prepared pan.
Bake until edges begin to pull away from sides of pan and a toothpick inserted in center comes out with just a few moist crumbs attached, 30 to 40 minutes.
Cool completely in pan.
Take cake out of pan by pulling on the tin foil on the sides, then cut into squares.
Serve plain, sprinkled with powder sugar or drizzle with white chocolate.