In a large bowl, whisk together pudding mix, milk and cool whip for 2 minutes. Let sit for another 5 minutes until it slightly thickens. 

Place a layer of graham cracker crumbs at the bottom of each jar (about 1/4 cup). Top with a layer of the thickened pudding mixture, then more graham cracker crumbs and another layer of pudding. 

To make the frosting, melt butter in a medium sauce pan over medium-low heat. Add cocoa powder and stir until combined. Remove from heat and alternate adding the powdered sugar and milk until combined. Add vanilla and stir (or whisk) until smooth. Spread over the final pudding layer. 

Chill in refrigerator for at least 3 hours before serving.