Line your 8x8 pan with parchment paper, letting some hang over the sides for easy removal.

In a saucepan on low heat, combine chocolate chips, sweetened condensed milk, and butter. Stir constantly until melted and smooth.

Once melted, turn off the heat and stir in vanilla, salt, and chopped walnuts.

Pour the mixture into the prepared pan, spreading it evenly, and top with additional walnut pieces if desired.

Chill in the fridge for 2 to 3 hours or until firm. Remove from the pan and slice into small squares.