Preheat your oven to 350°F (175°C) and grease a 9x9-inch baking pan.
Melt the butter in a medium saucepan over low heat.
Remove from heat and stir in sugar, eggs, and vanilla until well combined.
Add cocoa powder, flour, salt, and baking powder, mixing until just combined.
Fold in chocolate chips if using.
Pour the batter into the prepared baking pan and spread evenly.
Bake for 20-25 minutes or until a toothpick inserted comes out with a few moist crumbs.
Let the brownies cool in the pan for at least 10 minutes.
Lift the brownies out using the edges of the parchment paper, if used.
Cut into squares and serve warm or at room temperature.