1) In a medium saucepan, combine both kinds of sugar and the sour cream.
2) Over medium heat, cook, stirring, until sugar is dissolved.
3) Continue cooking, without stirring, to 238F on candy thermometer, or until a little in cold water forms a soft ball.
4) Remove from heat.
5) Add vanilla and walnuts.
6) Stir gently until all nuts are coated.
7) On a waxed paper, turn out the nuts and using a fork, speperate them.
8) Let dry.