This frosting goes great with the Chocolate Layer Cake that is listed here on CC.
Bittersweet Chocolate Frosting
1 1/2 cups sugar
6 Large egg yolks
1 tablespoon light corn syrup
1 1/2 cups whipping cream
6 ounces unsweetened chocolate
3 ounces semisweet chocolate
3/4 cup (1 1/2 sticks) unsalted butter, cut in to pieces, room temp.
1/2 teaspoon Vanilla Extract
Mix sugar, yolks and syrup in small bowl. Bring cream to simmerin heavy 3-quart saucepan. Add both chocolates and stir over low heat until smooth. Remove from heat. Stir in butter, then sugar mixture. Cook over low heat until mixture registers 165 – 170 degrees on candy thermometer, stirring constantly, about 10 minutes. Immediately pour mixture into bowl; do not scrapes sides of pan. Add vanilla.
Using electric mixer, beat frosting until cool. Let frosting stand at room temperature until think enough to spread, stirring occasionally, 1 1/2 hours.