Pre-heat the oven to 180℃/360℉. Line an 8x8" square baking pan.
Melt the dark chocolate by breaking up into small pieces in a bowl and heating for 30 second intervals in a microwave, stirring in between. Set aside to cool whilst making the brownies.
In a large bowl or the bowl of a stand mixer combine the melted butter, and both the brown and granulated sugars on a medium speed until totally combined. Add the eggs and vanilla and mix again. Add in the melted chocolate.
Fold in the flour and cocoa powder. Set Aside.