Line a 9x13-inch baking dish with parchment and lightly spray with non-stick spray. Set aside.
In the bowl of an electric stand-mixer, add the melted butter and cocoa powder. Using the paddle attachment, blend until smooth.
Add the flour and sugar. Beat together then add eggs and vanilla. Mix just until combined. Don't over mix. (Batter will be thick)
Pour batter into prepared baking dish and spread out evenly.
Preheat oven to 350° F.
Bake 25 to 30 minutes in preheated 350* oven until toothpick inserted in center comes out clean. Start testing at about 22 minutes.
Remove brownies from oven and let stand 10 minutes before frosting. You want the brownies still warm when you frost them!
FOR CHOCOLATE FROSTING: Beat together all the frosting ingredients until smooth. Pour and spread over warm brownies. Let cool completely before cutting and serving.