Try this recipe:
2 T. butter or margerine
1/4 C. cocoa
3 T. water
1/2 tsp. vanilla extract
1 1/4 C. powdered sugar
In small saucepan over low heat melt butter. Stir in cocoa and water. Cook, stirring constantly, until mixture thickens. DO NOT BOIL. Remove from heat. Stir in vanilla. Gradually add powdered sugar, beating with wire whisk until smooth. Add additional water, 1/2 tsp. at a time until desired consistency.
Good Luck and let me know how this turns out.