In a large bowl, combine popcorn and nuts; set aside. In a large saucepan, bring sugar, butter and corn syrup to a boil. Boil for 5 minutes, stirring occasionally.
Remove from the heat; add vanilla, cream of tartar and baking soda. Drizzle over popcorn mixture; stir to coat. Immediately spread onto two greased baking sheets; let dry for about 1 hour. Store in an airtight container.