Melt butter in a heavy saucepan over medium heat. Add sugars, salt, and corn syrup. Slowly add sweetened condensed milk. Cook mixture over medium-low heat, stirring constantly until mixture reaches exactly 235 degrees on your candy thermometer. Remove from heat and continue to stir for another minute. Add vanilla and mix well.
For sliced caramels, pour into a greased pan. Allow to cool before cutting.
For caramel popcorn, pour over your popcorn on parchment paper.
For caramel apples, I will share my tips and tricks on Wednesday.