Preheat your oven to 350°F (175°C). Grease a 9x9-inch baking pan or line it with parchment paper for easy removal.
In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, salt, ginger, cinnamon, and nutmeg until well combined.
In a large bowl, mix the melted butter, brown sugar, and granulated sugar until smooth. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract and molasses until fully incorporated.
Gradually add the dry ingredients to the wet ingredients, stirring until just combined. If using, fold in the chocolate chips.
Pour the batter into the prepared baking pan and spread it evenly. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Allow the brownies to cool in the pan for about 10 minutes before transferring them to a wire rack to cool completely. Cut into squares and serve.