Add the butter to a saucepan and melt on medium heat.
Pour the sugar and evaporated milk into the pan and mix well.
Turn the heat up to medium-high and bring to a boil, stirring occasionally.
Bring the temperature up to 234 degrees and remove from heat.
Add the marshmallow creme and mix until melted.
Next, add the vanilla extract and mix.
Add the chocolate chips to the saucepan and stir until melted.
Pour the fudge into a greased square 8" x 8" or 9" x 9" square dish and sprinkle with the sea salt.
Allow the fudge to set up for about four hours.
Cut into 1-inch squares and serve.