In a large bowl (or an electric stand mixer fitted with a paddle attachment), cream together the sweetened condensed milk and the cream cheese. In a separate bowl, combine the pudding and milk; whisk well. Working quickly, before the pudding has a chance to set, pour the pudding mixture into the bowl with the cream cheese mixture, and mix well to combine. Gently fold in the Cool Whip by hand.

Spray a 9x13-inch pan with non-stick spray. Place a single layer of graham crackers (leave the graham cracker sheets intact; no need to break them apart) on the bottom of the pan, and then spread a layer of half of the pudding mixture over the crackers. Add another graham cracker layer, and cover with the remaining pudding mixture before placing one final graham cracker layer on top. Refrigerate for 30 minutesr, until firm.

Place frosting in the microwave (make sure you have removed all of the foil liner first!) and, working in 8- to 10-second increments, cook the frosting to soften it, stirring after each increment. It should take approximately three increments to achieve the desired pourable consistency. Pour the frosting over the top graham cracker layer, and use a metal spatula to carefully spread the frosting over the entire top surface of the dessert to the edges of the pan. Chill at least 2 hours before serving.