Preheat the oven to 350°F (175°C).
In a medium saucepan, melt the butter over low heat. Once melted, remove from heat and stir in the sugar, eggs, and vanilla until combined.
In a separate bowl, whisk together the cocoa powder, flour, salt, and baking powder.
Gradually add the dry ingredients to the butter mixture, stirring until just combined. Do not overmix.
If using, fold in the chocolate chips for extra fudginess.
Pour the brownie batter into a greased 9-inch pie pan and spread it evenly.
Bake in the preheated oven for 30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Allow to cool for at least 15 minutes before slicing and serving.