Mix sugar, Karo and 1 cup of cream. Boil on stovetop until light brown, stirring often. Add the other cup of cream and cook until barely firm ball. {soft firm ball} Check at the soft ball stage on candy thermometer. If you cook too long it will be grainy. If you don't cook long enough it won't harden up.

Take off heat and stir in 1 cup walnuts and 1 tsp vanilla. Stir until it cools then pour into 8x8 dish with sides.