Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius). Grease an 8x8 inch baking pan or line it with parchment paper.
In a large bowl or the bowl of a stand mixer, add 1/2 cup melted butter with the 1/4 cup brown sugar and 3/4 cup granulated sugar. Mix with an electric hand mixer (or the paddle attachment of a stand mixer) until well combined.
Add 2 large eggs in one at a time, mixing well after each addition.
Add the 1 tsp vanilla extract and mix again.
Sift in the 1/3 cup cocoa powder, 1/2 cup flour, 1/4 tsp baking powder, and 1/4 tsp salt, and mix again until well combined.
Finally, add the 1/2 cup chocolate chips into the batter and mix by hand until evenly distributed.
Pour the batter into your prepared pan and spread it evenly.
Bake the brownies in the oven for 30 minutes until the edges are set and a toothpick in the center comes out with a few moist crumbs clinging to it.
All the brownies to cool completely before frosting.