My mom made these for us kids every year at Christmas, and I think I have made them for my family the past 26 years too!
- Preheat oven to 350º.
- Mix butter, sugar, egg yolk and vanilla. Add flour and salt; blend well.
- Spread into greased 13x9 pan. Bake about 15 minutes or until golden. Remove from oven.
- Immediately sprinkle chocolate chips over top. Cover pan with a second cookie sheet so chips will melt. Spread chocolate evenly when melted. Sprinkle with walnuts.
- Cut into squares while still warm. Refrigerate as needed to set chocolate. These cookies freeze well.