In a large mixing bowl, whisk together 3½ cups of cold milk and two boxes of instant vanilla pudding mix for about 2 minutes, until thickened and smooth. Fold in 8 oz of whipped topping until combined.

Place a layer of graham crackers in the bottom of a 9x13 inch baking pan and spread half of the pudding mixture evenly over the graham crackers.

Add another layer of graham crackers, pressing down gently. Pour the remaining pudding mixture over this layer, then top with a final layer of graham crackers.

Heat a 16 oz container of chocolate frosting in the microwave for about one minute at 50% power, until pourable. Drizzle over the top layer of graham crackers.

Cover the cake with plastic wrap and refrigerate for at least 8 hours or overnight to allow graham crackers to soften.

Remove from refrigerator, sprinkle with chocolate curls if desired, slice, and serve cold.