Ganache is basically chocolate butter. I know, that doesn't sound at all appetizing, which is fine. It just means there will be more for me. Ganache is often used to ice cakes, though it can also be cut into squares or rolled into balls and then dusted with cocoa or sugar to make chocolate truffles. (Yes, that's what a truffle is, ganache.)
3/4 cup (180 ml) heavy whipping cream
8 ounces (227 grams) chocolate (pick a chocolate that you like the flavor of, but it should lean toward semisweet or bittersweet)
2 tablespoons butter
1 tablespoon cognac or brandy
First break the chocolate into small pieces in the bottom of a bowl. Then bring the whipping cream (and butter if you choose to use it. apparently it makes the ganache shiny, though i make my ganache to eat, not to look pretty) to a boil.
Pour the whipping cream over the chocolate and (here comes the hard part) let it sit for about 5 minutes. (I'm always so tempted to start stirring, but when you stir too soon, you end up with a lumpier mixture.)
You can then use the ganache to ice a room temperature (or colder) cake or torte. (This recipe should cover one 9 inch cake.) Once the cake is iced, put it in the fridge for the ganache to harden.
Or, you can do what I do, pour the ganach into little bowls, set them in the fridge and pull them out to each straight later. :-)
If you'd like to make truffles, roll the cold ganache into balls (or cut it into squares) and dust cocoa (or some such) over them. Viola! That's all there is to it.