Preheat the oven 350-degrees. Line the bottom and sides of a 9x13 baking pan with foil so that it overhangs on all sides of the pan. This will allow you to pop it right out of the pan and you don't even need to grease it.
In a medium bowl, cream together the sugar and butter. Beat in the egg and vanilla until combined, then add in the pumpkin. At this point, the mixture does not look appetizing - in fact, it looks like you did something wrong - but don't worry, it will come together and be ok.
Mix in the dry ingredients until the mixture is creamy but thick.
Fold in the chocolate chips - I like using the milk and semisweet, but dark and white chocolate chips together would be tasty, too.
Spread the batter evenly in the prepared pan. Bake for about 35-40 minutes until the sides start to pull away from the sides. Cool completely in the pan, then refrigerate overnight – still in the pan.