1 c. butter
1 c. firmly packed light brown sugar
1 egg yolk
1 tsp. vanilla
2 c. sifted all-purpose flour
6 oz. semi-sweet chocolate (or more for thicker topping)
1 c. walnuts

In a large mixing bowl cream butter and sugar; beat in the egg yolk and vanilla. Stir in the flour. Spread thinly in a 13 x 9 inch pan; bake at 350 degrees for 15-20 minutes. Remove from oven. In the top of a double boiler melt chocolate; spread on cookie surface while still warm. Sprinkle with chopped walnuts; cut into squares when cool. Makes 40 squares.