2Combine the first 5 ingredients in pan and cook over med/low heat, stirring constantly until butter melts and sugar dissolves. Scrap sides making sure they are free of any sugar crystals.
3Attach a candy thermometer to pan, making sure it does not touch bottom of the pan.
4Increase your heat to medium and bring to a boil. Do not stir while syrup is boiling. (This is very important and also why you must be sure to have a large enough pan. Mixture will boil up and you will be inclined to stir it back down for fear it is going to overflow.)
5DO NOT STIR WHILE SYRUP IS BOILING! Your mixture will be whitish yellow at beginning, but by the time it has reached the proper temp it will be a dark caramel color.
6Continue to cook until syrup reaches soft ball state or 234-240 degrees on thermometer.
7Turn off heat, or remove from heat and add vanilla leaving thermometer in mixture.
DO NOT STIR IN THE VANILLA, until mixture cools to 200 degrees.
8Beat the fudge with an electric mixer set on medium until it is thick and no longer glossy.
9Stir in the nuts.
10Pour into a buttered 8 X 13 pan. Cool completely.
11Cut into 1 inch squares. Store in an airtight container in refrigerator.