In a medium saucepan, mix butter, brown sugar, and karo syrup. Bring ingredients to a boil.
Stirring constantly, boil for one minute.
Add sweetened condensed milk.
Boil 5 minutes (stirring constantly).
Remove from heat, continue stirring for 2 minutes.
Pour over desired amount of popcorn. (I used 5 bags of popcorn. If you don't want to make that much popcorn, store leftover caramel in fridge for future use.)
Recipe by A Mom's Take at https://www.amomstake.com/levana-caramel-popcorn-recipe/