Unwrap chocolate and chop or break into smaller pieces. Set aside.

In a large heavy pot put the evaporated milk, butter, sugar.

Bring butter, milk, sugar to a boil in large heavy pot on medium heat.

Once mixture starts boiling, cover and boil for five minutes.

Turn off heat: This is important. If electric stove, take off stove, remove to a protected surface. Add chocolate one piece at a time, and stir continuously. It will be a lot of stirring. As each piece melts, continue to add.

Important:The mixture will stay hot enough off the stove, but you must work quickly, and not stop stirring.

Once the last piece of chocolate is melted, add the marshmallow, and continue to stir.

When fully incorporated, stir in vanilla. Add nuts, if you are adding nuts. I often prefer without nuts.

IMMEDIATELY, pour into the pan, starting at one end and pouring to the other end. Shake pan. You have a few seconds to use a spatula to smooth out. STOP. It will have a wavy appearance. You do not want to manipulate the fudge, as the top dries and sets. Otherwise it will get a grainy appearance.

Allow to set for several hours until it's fully firm and cool. Cut into small pieces as this is rich fudge. It will stay several weeks in tins. You can also freeze.

Cover loosely with tin foil. Wait until completely set to cut. I usually wait overnight.

Cut into pieces. Store in tins. Fudge can be frozen, and sometime around January or February, when you get that chocolate craving, one bite does the trick.