Prepare cake as instructed and let cool.
Mix 1 cup cold milk with pudding mix,
Stir well until mix begins to thicken.
Pour mix into cool whip and gently stir together.
Spread over room temperature cake and refrigerate.
The frosting holds its shape extremely well and does not run. It is a little more difficult to get a perfectly smooth spread, so this is not the icing to use if that is the result you are going for. I also used this frosting on a hummingbird cake I made. Check it out here!