Dark Chocolate Frosting

We ate this at Mom's house on this cake. The frosting tastes like truffles.

• 1/2 cup plus 1 tablespoon unsweetened Dutch-process cocoa powder
• 1/2 cup plus 1 tablespoon boiling water
• 2 1/4 cups (4 1/2 sticks) unsalted butter room temperature
• 1/4 cup confectioners' sugar sifted
• 1/4 teaspoon salt
• 1 1/2 pounds best-quality semisweet chocolate melted and cooled

Directions

1. Combine cocoa and the boiling water, stirring until cocoa has dissolved. With an electric mixer on medium-high speed, beat butter, confectioners' sugar, and salt until pale and fluffy. Reduce speed to low. Add melted and cooled chocolate, beating until combined and scraping down sides of bowl as needed. Beat in the cocoa mixture. If not using immediately, frosting can be refrigerated up to 5 days, or frozen up to 1 month, in an airtight container. Before using, bring to room temperature, and beat on low speed until smooth again.

From Martha Stewart