This is my favorite ganache, which we used on our cakes at Wisconsin Cheesecakery. This ganache also makes wonderful truffles when chilled and can be flavored with almost anything you can dream up. For Valentine's Day I'm making Pomegranate Truffles, and I'll post the recipe later this week once I get the quantities figured out.
This recipe is enough to top one cake. If you are making more, or making truffles, increase the quantities accordingly.
3 oz heavy cream
3 oz dark chocolate in chunks (I recommend using a high quality dark chocolate, at least 60% cacao for better flavor)
Heat cream to just before boiling, stirring constantly to keep from forming a skin. Pour hot cream over chocolate and stir to combine until smooth. If using to top a cake, be sure the cake is chilled before topping and then refrigerate to set the ganache. If using for truffles, chill until firm, then scoop out into truffles and coat with cocoa, nuts, melted chocolate, etc.