Preheat oven to 250°F. Mix sugar, apple pie spice and salt in small bowl. Beat egg white and vanilla in medium bowl until foamy. Add walnuts; toss to coat. Add spice mixture; toss to coat nuts evenly.
Spread walnuts in single layer on lightly greased baking sheet.
Bake 1 hour, stirring after 30 minutes. Cool slightly and break apart. Cool completely. Store in airtight container up to 2 weeks.