Butter a square 8" pan, line with parchment. Set aside.

Melt butter in a large glass mixing bowl. Add sugar, corn syrup, and sweetened condensed milk. Cook 3 minutes, stir, cook 3 more minutes.

Spoon a bit of the caramel into a cup of ice cold water. If it can be rolled into a soft ball, it's ready.

Stir in the vanilla and salt.

Pour into prepared pan and let sit till completely cooled.

Cut into rectangle or square shaped pieces and wrap in waxed paper.