Line a 9"x 9" square baking pan with foil. Grease foil lightly (I use butter for this) and set pan aside.
Combine butter, sugar, evaporated milk, and salt in a large saucepan. Cook over medium heat until sugar dissolves. Stir the mixture occasionally, until it comes to a rolling boil. Then reduce the heat slightly, and boil, stirring constantly for 5 minutes.
Remove from heat.
Add marshmallow creme, chocolate chips, and vanilla extract. Beat with an electric mixer until well mixed.
Spread in prepared pan, and chill for 2-3 hours (or until firm) in the refrigerator.
Remove fudge from pan (by lifting the foil out of the pan), and peel off the foil.
Cut into small squares.
Notes
You can also add about 1/2 cup chopped walnuts to this recipe. Stir them in just before spreading fudge mixture into the pan.This recipe makes about 2 1/2 pounds of fudge.