Preheat the oven to 350 degrees F (see note above about oven temperature). Line a large, rimmed baking sheet with parchment paper or silicone liners.
In the bowl of a stand mixer fitted with the paddle attachment or using a handheld electric mixer, cream together the butter, brown sugar and granulated sugar until light and fluffy, 2-3 minutes. Add the vanilla, pumpkin, and water, and mix until combined.
In a separate bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, nutmeg and allspice.
Add the dry ingredients to the batter and mix until combined. Stir in the chocolate chips.
The dough will be very soft. Use a spoon or cookie scoop (I use my #40 cookie scoop) to drop the cookie dough by heaping tablespoonfuls onto the prepared baking sheet.
Bake for 10-11 minutes until the edges are set but the middles are still a little bit soft. When the cookies come out of the oven, lightly tap or drop the cookie sheet on the counter (this helps the thinner/chewy factor of the cookies but you won't get fired if you don't do it). If the cookies were taken out while still soft in the center, they'll flatten more as they cool. Let them cool 3-4 minutes on the baking sheet before removing to a wire rack to cool completely.
Repeat with remaining dough.
These cookies taste great the day of, even better the next day, and they freeze great!
Notes
Pumpkin Puree: when it comes to pumpkin puree, I've found all types (homemade and storebought) work fine in this recipe with this caveat: the recipe was written using Libby's brand since it's probably the most widely available overall. If using homemade pumpkin puree, which tends to be a little softer, omit the water. Same goes for the Trader Joe's brand of pumpkin puree and other canned brands that are very soft and more watery.Flour: it's really, really important not to overflour the cookie dough in this recipe or you'll end up with puffy, cakey cookies instead of thinner cookies. If you don't have a scale, fluff the flour really well before scooping into the measuring cup and leveling off.Oven Temp: If you bake a sheet of cookies and find they are too puffy, decrease the oven temperature to 325 degrees (it might be that your oven bakes hotter than mine which will make for a puffier cookie).Making it Even Quicker: also, in the interest of full disclosure, I've made these cookies SO many times, and often, I just throw the dry ingredients into the bowl with the cookie batter without whisking them together in another bowl first. Cookie dough rebels unite.