Pour the milk into a large saucepan and turn on low heat.
Sprinkle in the salt, then add the chocolate chips.
Stir continuously, allowing the chocolate chips to melt into the mixture.
Remove from heat.
Quickly stir in the butter until its completely melted, and then stir in the vanilla.
Fold in the marshmallows with a rubber spatula, making sure they are completely covered with the chocolate.
Line a square baking pan with wax paper or foil extending over the edges.
Spread the mixture into the prepared pan.
Place the fudge into the refrigerator two hours or until firm.
Remove the fudge by using the wax paper edges.
Cut the fudge into bite size servings.
Serve or wrap for gifting.