Combine butter, brown sugar, sweetened condensed milk, corn syrup, and salt in a heavy-bottomed saucepan over medium heat. Bring to a boil, stirring constantly.
Heat to between 235 and 240 degrees F (Soft Ball Stage), or until a small amount of the mixture dropped into cold water forms a soft ball that flattens when removed from the water and placed on a flat surface. Cook for 2 minutes at that temperature.
Remove from the heat and stir in vanilla.
Add parchment paper to a 9x13 pan.
Pour caramel mixture into pan and allow to cool completely.
Remove from pan and cut caramels into 1 inch squares by using a sharp butter coated knife or butter coated bench scraper.
Wrap caramels in 5x5 in pieces of wax paper or cellophane and refrigerate until ready to serve.
