This ganache thickens as it sits; you want it pourable but thick enough to coat the cake.
Martha Stewart Living, December/January 1993/1994
Yield Makes about 1 1/2 cups
9 ounces bittersweet or semisweet chocolate, finely chopped
1 1/2 cups heavy cream
Place chocolate in a medium bowl. Heat cream in a small saucepan until bubbles begin to appear around edges (scalding); pour over chocolate. Let stand 5 minutes, then stir until smooth. Set aside at room temperature until cool but pourable, stirring occasionally.