Spread walnuts in a single layer on a baking sheet. Bake at 350° for 5 minutes or until heated through. Cover and keep warm.
In a large heavy saucepan, combine the sugar, coffee, cinnamon and salt. Bring to a boil over medium heat. Cook, without stirring, until a candy thermometer reads 250° (hard-ball stage). Remove from the heat; stir in vanilla. Add warm walnuts; toss to coat.
Pour into a greased 15x10x1-in. pan; separate with a fork. Cool. Store in an airtight container in the refrigerator.