If you want to give this frosting extra flavor, add a teaspoon of mint, orange, or coffee extract after the chocolate has been incorporated. To frost a four-layer cake you will need to increase the ingredients accordingly: use 24 ounces chocolate, 4 1/2 sticks butter, 3/4 cup sugar, and 1/2 cup plus 1 tablespoon each cocoa and boiling water. Alternatively, halving this recipe makes just enough for a standard sheet cake or a dozen cupcakes.

　　

Ingredients

makes about 5 cups

　　1 pound best-quality semisweet chocolate, finely chopped

　　6 tablespoons Dutch-process cocoa powder

　　6 tablespoons boiling water

　　3 sticks (1 1/2 cups) unsalted butter, room temperature

　　1/2 cup confectioners’ sugar

　　Pinch of salt

　　

Step 1

Place chocolate in a heatproof bowl set over (but not touching) simmering water. Turn off the heat; stir occasionally until chocolate has melted completely, about 15 minutes. Set bowl on countertop, and let chocolate cool to room temperature, 25 to 30 minutes. Meanwhile, combine cocoa powder and boiling water in a small bowl; stir until cocoa is dissolved.

　　

Step 2

In the bowl of an electric mixer fitted with the paddle attachment, beat butter, confectioners’ sugar, and salt on medium-high speed until light and fluffy, 3 to 4 minutes. Add melted chocolate; beat on low speed until combined, 1 to 2 minutes, scraping down the sides of the bowl as needed. Beat in the cocoa mixture.

　　Reprinted with permission from Martha Stewart's Baking Handbook by Martha Stewart. © 2005 Clarkson Potter