Put milk, chocolate, marshmallows, and salt in a heavy saucepan. Stir over medium heat until chocolate and marshmallows melt completely and mixture thickens.
Take off heat and cool to room temperature.
Line a 9″ pie pan with vanilla wafers.
Layer a pint of vanilla ice cream over the wafers.
Cover ice cream with half of chocolate mixture.
Repeat with another pint of vanilla ice cream and the rest of the chocolate mixture.