Preheat your oven to 350°F (175°C). Grease an 8x8-inch baking pan or line it with parchment paper for easy removal.
In a medium bowl, whisk together the cocoa powder, flour, salt, and baking powder until well combined. Set aside.
In a microwave-safe bowl, melt the butter. Once melted, stir in the sugar until well mixed.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. Be careful not to overmix. If using, fold in the chocolate chips.
Pour the batter into the prepared baking pan and spread it evenly.
Bake for 20-25 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Do not overbake for the best fudgy texture.
Allow the brownies to cool in the pan for at least 10 minutes before cutting into squares.