Preheat oven to 350 degrees F. Lightly grease a 9x13-inch pan; set aside.

In a large mixing bowl, cream the butter and sugar on medium-high speed until light and fluffy. Add the egg and beat until combined. Stir in the vanilla and pumpkin puree and mix until fully combined. Do not worry if the mixture is somewhat curdled at this point. This is normal.

In a separate medium bowl, mix the flour, pumpkin pie spice, baking soda and salt in a medium bowl. Whisk to combine. Gradually add to the wet ingredients while mixing on low speed until just combined. Fold in the chocolate chips.

Pour the batter into the prepared pan and spread evenly. Bake for 35 to 40 minutes, until passes the toothpick test. Remove from oven and completely cool in the pan before cutting and serving.

Source: Adapted from Two Peas and Their Pod, originally from Martha Stewart