Perfect fudge every time, just don't forget to use the candy thermometer! If you overcook, the fudge will be crumbly and dry and if you undercook, you'll be serving it on a spoon. So, timing is everything, as usual!
Mix sugar and chocolate into a 3 quart heavy saucepan.
Add corn syrup and evaporated milk and cook over a medium heat until sugar dissolves and mixture begins to boil. Then cover and cook for two minutes.
Uncover and continue cooking until candy thermometer reaches 234 degrees or soft ball stage while stirring occasionally. Critical point is not to overcook or undercook and use a reliable candy thermometer.
Remove from heat, add butter and vanilla but do not stir, and let cool until candy thermometer reaches 110 degrees. Sometimes I sit the saucepan in cold water(in the sink)which allows faster cooling time.
When cooled, beat the mixture with a large wooded spoon until it loses its gloss and thickens. Add chopped nuts at this time. Pour into an 8x8 inch buttered pan and cut into squares when hardened.