This is my mothers recipe. The only one I'll use. If you don't cook it to 230, more like 220 you will have a lovely caramel sauce instead of caramels. (My mom lives in a higher altitude and her caramels must reach 242 degrees to be firm enough.)
In a heavy sauce pan stir together the sugar, karo and 1 c of cream.
Cook on medium to medium high stirring almost constantly till it reaches about 235 degrees on a candy thermometer. To test, place cold water in a cup and drop about 1 teaspoon of the mixture into it.if the mixture can be formed into a soft ball with your fingers it is ready.
While stirring constantly add the other cup of cream very slowly. Cook till temp reaches bout 235 again.
Remove from heat and stir in butter and vanilla. If you desire nuts stir the in now.
Pour into a lightly buttered 9 by 9.
Allow to cool.
Cut into squares and wrap in wax paper or keep in pan and cover with plastic .