Preheat oven to 350 degrees.

Line bottom and sides of a 9-by-13-inch baking pan with foil, leaving an overhang on all sides. Spray foil and sides of pan with cooking spray.

In a medium bowl, whisk together flour, pie spice, baking soda, and salt; set aside.

With an electric mixer, cream butter and sugar on medium-high speed until smooth; beat in egg and vanilla until combined. Beat in pumpkin puree (mixture may appear curdled). Reduce speed to low, and mix in dry ingredients until just combined. Fold in 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.

Lift cake from pan (using foil as an aid). Peel off foil, and use a serrated knife to cut into squares.