Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan or line it with parchment paper for easy removal.
In a large mixing bowl, melt the butter in the microwave or on the stovetop. Let it cool slightly.
Once cooled, whisk in the granulated sugar until smooth and well combined.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix.
If using, fold in the chocolate chips until evenly distributed.
Pour the batter into the prepared baking pan and spread it evenly.
Bake in the preheated oven for 25 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Allow the brownies to cool in the pan before cutting them into squares.