Chop. Pour. Stir. Those three basic steps are all there is to making an irresistible batch of ganache. Despite its French name, ganache is nothing elaborate -- chopped chocolate melted in heated heavy cream, with just a bit of salt to bring out the flavor -- and it can be used in a multitude of ways.
While it's still warm, ganache can be poured directly from the bowl over a cake for a can't-fail glaze. Or piped into tartlets. Or it can be cooled to room temperature and whipped into a fluffy frosting or whoopie pie filling. Mixed with some peanut butter, chilled, and rolled, it turns into truffles.
Our basic ganache recipe (which can easily be multiplied) is the base for all the variations that follow. First, coarsely chop 8 ounces of semisweet or bittersweet chocolate (we like 61 percent cacao). A serrated knife is best for the job; its sawlike teeth grab the chocolate, breaking it up.
If the fat starts to separate from the cream, much like the oil in a vinaigrette, fret not. To bring a "broken" ganache back, whisk in water, 1 tablespoon at a time, until the mixture is smooth and emulsified again. Resist the impulse to add cream, which will disrupt the ratio of chocolate to fat (generally, one ounce chopped chocolate for every fluid ounce of heavy cream -- plus 1/8 teaspoon coarse salt for every eight ounces chocolate).
Ganache that has cooled to room temperature can be used as a whipped filling. As it cools, stir often for 45 minutes to 1 hour. Beat it with a mixer on medium-high speed until paler and fluffy, 2 to 4 minutes. (1 1/2 cups ganache will yield about 2 cups when whipped.) Transfer to a disposable pastry bag with a large opening and use it as a filling for mini whoopie pies.