Preheat oven to 350 degrees Fahrenheit (176 C). Line a 9 x 13-inch baking sheet with parchment paper or butter and lightly flour. Set aside.  Melt butter in a small pan.  Set aside.  In a large mixing bowl, stir together sugar, flour, cocoa, and salt.  Add melted butter and mix just until blended.  Add eggs and vanilla,mix well. Stir in toasted walnuts and chocolate chips.  Carefully spoon batter into prepared pan.  Bake for 25-27 minutes being careful not to over bake.  Remove from oven and allow to cool before cutting into squares.