Melt the butter in a saucepan on medium-high heat.
Add the evaporated milk and sugar and stir.
Bring to a full rolling boil on medium, stirring constantly. Cook until the candy thermometer reaches 234-degrees or for 4 minutes.
Remove from heat.
Add marshmallow cream. Stir until blended.
Add vanilla. Stir.
Add chocolate chips and stir until blended.
Add walnuts (optional).
Pour into pan and cool.
