Heat cream and confectioners' sugar in a saucepan just to a simmer. Remove from heat and pour over chocolate in a mixing bowl. Let sit 5 min, then whisk until smooth. Add the vanilla.
Set the bowl of ganache over another bowl filled with ice and water (an ice bath), and allow mixture to cool, stirring occasionally. (Stir until ganache is cold to the touch, about 5 minutes.)
Whip ganache in a mixer until lighter in color and just fluffy or aerated (don't over whip or ganache will curdle). Use immediately.
Notes
Don't over whip this frosting or it will curdle. Cut this recipe in half if you just need 2 cups for cupcakes or filling.Nutrition Facts are for 1 cup of whipped chocolate ganache.