– Add beaten egg yolk, vanilla, and sifted flour and mix well.– Press onto ungreased 13"x18" cookie sheet (with edges) with your fingers. It should go to the edge.– Bake at 350° for 15-20 minutes or until slightly golden brown.
– Upon removing from the oven, sprinkle milk chocolate chips on top. To keep heat in, cover with aluminum foil. Let them melt for about 5 minutes and then spread evenly across top.– Sprinkle with walnuts.– Cut into squares while cookies are warm.