Using a heavby gauge pan, combine sugar, corn syrup and half and half. Stir until sugar is dissolved.
Bring to a boil over low heat. Boil for 10 minutes.
Add evaporated milk a little at a time.
Add in butter.
Bring back to a boil and cook until a candy thermometer reaches 243 degrees Stir now and then. Stir more the closer it gets to the desired tempeature. Mixture will thicken and turn golden brown
Remove from heat and stir in vanilla.
Pour into 2 8 x 8 butter pans and allow to cool and set up
When cool, cut into pieces and wrap in wax paper.