In a large bowl combine the melted butter, and cocoa powder. Mix until they are combined and it is nice and smooth.
Beat in eggs, sugar, and vanilla until the eggs are fully incorporated.
Stir in the flour and salt until just combined, and the flour streaks have just disappeared. Fold in the chocolate chips.
Pour into prepared pan. Bake for 25 minutes, or until a tester comes out clean. The edges will be set and starting to crack.
Remove from oven, and cool completely.
Meanwhile, prepare the frosting by, mixing everything except the chocolate chips together until you get a spreadable consistency. Adjust the sugar and milk as necessary.
Fold in the chocolate chips to the frosting.
Once brownies have completely cooled, spread the frosting evenly over the top of the brownies.