Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan.
Melt the butter in a medium saucepan over low heat.
Remove from heat and stir in sugar, eggs, and vanilla.
Mix well until combined and smooth.
Add in the cocoa, flour, salt, and baking powder.
Stir until just combined; do not overmix.
If using, fold in chocolate chips for extra fudginess.
Pour the brownie batter into the greased pan and spread evenly.
Bake for 25-30 minutes, or until a toothpick comes out with a few moist crumbs.
Let cool before cutting into squares and serving.