My son just went off to Penn State, so I'm making Mud Bars to send to him. He loves college, but the cafeteria food is another matter....
I had my own bakery before, and here is the ganache that I used:
1 lb. semisweet chocolate
Melt these together, then chill. I would stir it every half hour or so. Once it gets very thick and spreadable, ice the cakes immediately. This will give you a heavy, fudge-like icing. You can also beat it, as PBSF does, but it will change the texture to a lighter one. Here's a hint, you can actually ice the cake with the heavier, unwhipped icing, keeping some of the icing back. Then whip the remaining icing, and pipe rosettes on the cake. It will look as if two different icings were used.
Also, you can make a poured ganache by using it when it is still liquid, placing the cake on a rack over a pan, and pouring the ganache over it. It will be thin, but beautifully smooth. It works great over a layer of almond paste.