Similar to dark chocolate frosting (page 302), this topping gets its intense color from the addition of semisweet chocolate. Sour cream and cream cheese impart tangy flavor and ultra-creamy consistency. This frosting would pair well with any chocolate cupcake, particularly devil’s food (page 34; also made with sour cream), as well as those made with banana, such as the roasted banana cupcakes on page 141.

Ingredients

　　1 pound (4 cups) confectioners’ sugar, sifted

　　1/2 cup unsweetened Dutch-process cocoa powder

　　1/4 teaspoon salt

　　12 ounces cream cheese, room temperature

　　3/4 cup (1 1/2 sticks) unsalted butter, room temperature

　　18 ounces bittersweet chocolate, melted and cooled (see page 323)

　　1 1/2 cups sour cream

　　Sift together confectioners’ sugar, cocoa, and salt. With an electric mixer on medium-high speed, beat cream cheese and butter until pale and fluffy. Reduce speed to low. Gradually add sugar mixture; mix until combined. Mix in melted and cooled chocolate and then sour cream; scrape down sides of bowl and continue beating until smooth. Use immediately, or frosting can be stored in the refrigerator 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.

　　Martha Stewart's Cupcakes