This is a sure set fudge. I know I have tried some and they won't set but this one is very easy. I always fix my fudge in a heavy duty pan that is nice and thick. It is very easy for fudge to stick and burn if you don't. I use the pot part of an old small pressure cooker. It works well for that.
Mix together sugar, butter and milk. Cook on medium heat constantly stirring. Once mixture comes to a rolling boil, cook for 5 minutes and stir to make sure it doesn't scorch.
After 5 minutes remove from heat and add marshmallow cream, peanut butter, vanilla and nuts. Mix well and continue to beat by hand until it starts to thicken. Pour in a well greased and foil lined square pan. Once cooled completely, turn over on cuttin board. Peel off the foil and cut up into squares and store at room temperature in air tight tupperware.
If you do use crunchy peanut butter there is no need of adding any nuts.