Preheat your oven to 350°F (175°C). Grease the baking dish or line it with parchment paper.
In a medium saucepan, melt the butter over low heat. Remove from heat and stir in the granulated sugar, eggs, and vanilla extract until well combined.
In a separate bowl, whisk together the cocoa powder, flour, salt, and baking powder.
Gradually add the dry ingredients to the wet mixture, stirring just until combined. Do not overmix.
Fold in the chocolate chips, if using.
Pour the batter into the prepared baking dish, spreading it evenly.
Bake in preheated oven for 20 to 25 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Avoid overbaking for fudgy texture.
Allow the brownies to cool in the pan for at least 10 minutes before cutting them into squares.