4 tablespoons unsalted butter, cut into tablespoons
1 1/2 cups confectioners' sugar
1/4 cup boiling water
In a small saucepan, melt the chocolate with the butter over moderately low heat. Whisk in the sugar, then stir in the boiling water until smooth. Remove from the heat. Place a piece of plastic directly on the surface of the glaze and keep warm until ready to use.