In a large saucepan, combine all of the ingredients except the vanilla and walnuts. Cook over medium heat, stirring constantly, until the sugar has dissolved.
Bring the mixture to a boil, stirring constantly, for 2 minutes.
Remove from the heat and stir in the vanilla and walnuts.
Beat the mixture with a wooden spoon for 7 minutes until it thickens.
Quickly spread the fudge into the prepared pan and cool until completely hardened. Cut into 1½ inch squares.
Recipe by Culinary Thymes at https://www.culinarythymes.com/walnut-fudge-squares/