Frosting help....

My mother(now gone) use to make a cake frosting with Hershey's cocoa that would set up hard on top of pan cake.She use to cook it on top of the stove and us kids would fight over who got to eat the leftovers out of the pan with the spoon. Any body know of this kind of frosting.Always ended up shiny and smooth and soooooo good.She used the same kind for brownies, only a little thicker. HELP?? :-)