1. Start with 10 cups of popcorn (either air popped or microwave). Lay popcorn on a large jellyroll pan lined with nonstick foil.
2. In a pot, melt:
1/2 cup butter
Add:
1 cup light brown sugar
1/4 cup light corn syrup
1/2 tsp. salt
Stirring all to combine, bring to a boil and then boil without stirring for 4 minutes.
Remove from heat and add:
1/4 tsp. baking soda
1/2 tsp. vanilla
Pour over the popcorn stirring well to coat. Bake at 250 degrees for 1 hour, stirring every 15 minutes. Remove, cool and break into pieces.