Try this one out and let me know if it works out for you:
Fudge Icing:
• 4 ounces margarine
• 1/2 cup pareve milk
• 1/2 cup cocoa powder
• 1 pound confectioners' sugar
• 1 teaspoon vanilla
In a saucepan, over medium heat, combine the margarine and milk. Bring to a boil. Sift the confectioners' sugar and cocoa powder into a large bowl. Add the butter mixture and whisk well. Add the vanilla.