Bring first 5 ingredients to a boil in a saucepan over medium heat, stirring constantly.
Reduce heat to medium-low and simmer 5 minutes.
Remove from heat and stir in ¼ teaspoons baking soda.
Combine popcorn and nuts in a lightly greased roasting pan.
Pour sugar mixture evenly over popcorn.
Using a lightly greased spatula, stir well to coat.
Bake at 250 degrees for 1 hour, stirring every 15 minutes.
Spread on wax paper to cool, breaking apart large clumps as mixture cools.
Store in airtight containers.