Combine butter, cocoa, and milk in medium saucepan. Cook over low heat 5 minutes or until margarine melts. Bring to a boil over medium heat. Remove from heat, and stir in sugar, vanilla, and pecans. Beat at medium speed with an electric mixer until smooth and sugar dissolves.
This was very easy. Instead of pecans I added one cup of pnut butter. It soaks into the cake and is even better the next day!