1 c. butter
1 c. brown sugar
1 tsp. vanilla
2 c. flour
1 egg yolk

Mix and press in a 9 x 13 inch pan that has been buttered and floured. Bake at 350 degrees for 25 minutes. When you take it out of the oven, sprinkle one 6 ounce package chocolate chips. Spread smooth when glassy.