In a medium saucepan over medium heat, combine brown sugar, white sugar, cream, corn syrup and salt. Stir until sugar is dissolved. Heat to between 234 and 240 degrees F (112 to 116 degrees C), or until a small amount of syrup dropped into cold water forms a soft ball that flattens when removed from the water and placed on a flat surface.
Pour in vanilla and beat until creamy. Stir in nuts. Pour into prepared pan.
Let cool completely before cutting into squares.