Preheat the oven to 350°F. Line baking sheets with parchment paper or silicone baking mats.
In a large bowl, combine 1 cup canned pumpkin, 1 cup white sugar, 1/2 cup vegetable oil, 1 large egg, and 1 tablespoon vanilla extract. Mix until smooth and well combined.
In a separate bowl, whisk together 2 cups all-purpose flour, 2 teaspoons baking powder, 1 teaspoon ground cinnamon, 1/2 teaspoon pumpkin pie spice, and 1/2 teaspoon salt.
In a small bowl, stir 1 teaspoon baking soda into 1 teaspoon milk until dissolved.
Add the milk and baking soda mixture to the pumpkin mixture and stir until combined.
Gradually add the dry ingredients to the wet ingredients. Mix just until combined. Do not overmix.
Fold in 2 cups chocolate chips until evenly distributed throughout the dough.
Drop the dough by spoonfuls onto the prepared baking sheets, spacing the cookies about 2 inches apart. Add a few extra chocolate chips to the tops, if desired.
Bake for 10 to 11 minutes, or until the cookies are set and a toothpick inserted into the center comes out clean.
Let the cookies cool on the baking sheet for 2 minutes, then transfer them to a wire cooling rack to cool completely.