Fudge Frosting

    1/2 cup butter

    3 (1 ounce) squares unsweetened chocolate

    1 pound confectioners' sugar

    1/2 teaspoon vanilla extract

    3/4 cup milk

1. Melt chocolate and butter in the microwave, or in the top of a double boiler. In a large bowl, combine confectioners' sugar, vanilla and 1/2 cup of the milk. Blend in the melted chocolate mixture. Add remaining milk, a little at a time, until desired consistency is achieved.
2. Let stand until spreadable (frosting will thicken as it cools).

From: http://allrecipes.com/recipe/8486/carolines-chocolate-fudge-frosting/