My family has been making this recipe since the late 60s. It is a must make at Christmas time. This recipe was on the back of either the Carnation evaporated milk can or the back of the Nestles chocolate chip bag. It was before the time of Marshmallow creme in the jar.
In a heavy 2 qt saucepan add sugar, butter, evaporated milk, marshmallows and salt. Cook stirring constantly over medium heat to a boil. Mixture will be bubbling all over top. Boil and stir for 5 minutes more. Take off heat.
Stir in until completely melted, chocolate chips, vanilla and nuts (if using).
Spread into a buttered 8 inch square pan. Cool and cut into 30 pieces.
Remember this is the original recipe. I no longer use a heavy 2 qt saucepan...just a regular 2 qt sauce pan. It is important to keep stirring after things are melting as that is when it can burn. The stirring is worth it tho as this is the best recipe! If you dont boil it for a full five minutes it wont set up and it will taste grainy.