Instructions:

In a glass 9x13 pan, lay graham crackers in squares. Beat pudding mix and 2 cups milk until thickened, fold in Cool Whip. Add 1/2 pudding over graham crackers; add another layer of graham crackers. Add rest of pudding, layer more graham crackers over this. In a saucepan, add cocoa, sugar and evaporated milk. Bring to a boil; cook 1 minute, stirring constantly. Add butter and vanilla; let cool slightly. Pour over graham crackers; chill at least 12 hours before serving.