Preheat the oven to 350 and line a 9x13 baking dish with aluminum foil. Spray the foil with cooking spray.
Melt two sticks of butter, and mix with cocoa powder with electric mixer until smooth.
Add the sugar and flour and mix.
Add eggs and vanilla and mix again.
Pour the batter into the baking dish and bake for 25 minutes.
While the brownies cool, make the frosting.