1 1/2 (1 ounce) squares unsweetened chocolate
1/4 cup butter
1 1/2 cups confectioners' sugar
1 egg white
1 teaspoon vanilla extract
Melt chocolate and butter in small heavy saucepan over low heat; stir to blend. Beat in powdered sugar. Beat in egg white and vanilla, adding a little water, if necessary, to make smooth, slightly soft frosting. Spoon over Chocolate Frosted Marshmallow Cookies cookies to cover marshmallows.