Add the wafers to a piping bag. Microwave at 15-second intervals, squeezing the mixture to stir it together, until mostly melted. Squeeze to mix until fully melted. You want the mixture to be a marbled. Pipe into the chocolate mold. Let rest to firm up for at least an hour.
Add the cold milk to a bowl and whisk in the pudding mix until well combined. Chill in the refrigerator for 15 minutes. Mix in the whipped topping.