1. Combine both kinds of sugar and the sour cream in large saucepan. Cook over medium heat, stirring, until sugar is dissolved.
2. Continue cooking without stirring to 238°F. on candy thermometer, or until a little in cold water forms a soft ball. Remove from heat.
3. Add vanilla and nuts. Stir gently until all nuts are coated.
4. Turn onto waxed paper; with a fork, separate the nuts. Let dry.