Preheat your oven to 350°F (175°C) and grease the 9x9 inch baking pan.
In a large mixing bowl, combine the pumpkin puree, brown sugar, granulated sugar, vegetable oil, eggs, and vanilla extract. Whisk until the mixture is smooth and well combined.
In another bowl, sift together the all-purpose flour, cocoa powder, baking powder, baking soda, salt, cinnamon, nutmeg, and ginger.
Gradually add the dry ingredients to the pumpkin mixture, stirring until just combined. Be careful not to overmix.
If using, gently fold in the chocolate chips.
Pour the batter into the prepared baking pan and spread it evenly using a spatula.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs (not wet batter).
Allow the brownies to cool in the pan for 10-15 minutes before cutting them into 12 squares.