Step 1

Prepare the filling by combining pudding mix and milk. Beat. Stir in Cool Whip.

Step 2

Place a layer of graham crackers in bottom of a 9x13 dish. Spread 1/2 filling mixture on top. Repeat with another layer of graham crackers, add rest of filling, top with final layer of graham crackers.

Step 3

To make the topping, bring cocoa, milk and sugar to a roiling boil. Let topping boil for one full minute, stirring frequently.

Step 4

Remove from heat, cool 1 minute.

Step 5

Add butter and vanilla to topping, and stir till butter is melted.

Step 6

Pour chocolate topping over graham crackers and refrigerate overnight.