For cake, blend all ingredients with a mixer and pour into three 9-inch cake pans that have been well greased and floured. Cook at 350 degrees for 25-30 minutes.
For filling, pour the Hershey bars from the food processor into a small bowl and set aside. In a large bowl, beat the cream cheese and sugars. Blend until it's not quite so grainy, for about 2-3 minutes. Fold the Cool Whip into the cream cheese mixture.
Blend chopped Hershey bars into the cream cheese mixture. Frost the cake and decorate as desired.