Pop corn and remove old maids. Spread corn in a large flat pan, and preheat in a 250° oven
In a saucepan, melt butter, and stir in brown sugar, corn syrup and salt. Stir constantly until mixture comes to a boil. Continue to boil without stirring for about 5 minutes (240°). Remove from heat, and add baking soda and vanilla, stirring until foamy. If nuts are used, add them NOW, stirring until heated through, and no longer clumped up.
Pour syrup mixture over preheated popcorn, and stir to coat. Bake for about 30 minutes, stirring 2 or 3 times to evenly distribute the coating.
Bake longer, about 60 minutes, for a more Cracker Jack taste. Cook, break up and store airtight.