These are the cookies of my childhood.
Whenever there was a bake sale or school party, when my sister and I were children, these were the cookies my mother would bake, because they taste wonderful and couldn't be easier to make.
1 Cup softened butter
1 Cup firmly packed brown sugar
1 egg yolk
1 teaspoon vanilla
2 Cups sifted flour
8 ounces milk chocolate bar, broken into pieces
1/4 cup chopped walnuts
Pre-heat oven to 350 degrees F.
Cream butter and sugar together. Blend in egg yolk and vanilla. Add flour; mix well. Spread in a greased jelly roll pan (15 1/2 by 10 1/2 inches). Bake for 15-20 minutes. Remove from oven; place broken pieces of chocolate bar on hot base. When melted, spread evenly. Sprinkle with walnuts. When they the cookies are cool, cut into squares or rectangles.