Make the pudding mixture

• Whisk the cold milk and instant pudding mix in a bowl until thickened.
• Fold in the whipped topping until smooth.

Melt the frosting

• Microwave the chocolate frosting in short bursts, or heat it in a saucepan, just until pourable.

Layer the cake

• In the cake pan, layer graham crackers, then pudding mixture.
• Repeat the layers, finishing with a final layer of graham crackers.
• Pour the melted chocolate frosting evenly over the top.

Chill and serve

• Refrigerate until the crackers soften and the cake sets before serving.