Combine butter, sugar, and evaporated milk in a heavy bottomed saucepan.
Bring to a full rolling boil over medium heat. Stir continuously.
Continue boiling for 4 minutes on medium heat. Make sure and stir constantly so mixture doesn't burn!
Remove from heat. Gradually stir in cocoa powder and chocolate chips until melted and smooth. Add in the marshmallow creme, vanilla extract, and chopped nuts and mix very well until fully combined.
Immediately pour into a greased 9x13" baking pan. Cool at room temperature before cutting into squares. Enjoy!