Work butter into flour on well-floured surface until granular. Add one half cup powdered sugar, 3 egg yolks, a little rum(or extract)for flavor to taste, and lemon peel. Knead ingredients into dough on a floured board about ten min. Roll out to a thickness of 1/8" and cut into different shapes or circles about 1-1/2"in dia. Stir 1 cup powdered sugar into 3 stiffly beaten egg whites for about 5 min. Then add vinegar. Mix well. Put a little of this mixture on top of

each piece of dough and set on cookie sheet. Bake in a moderate oven 350 until light brown. While still warm place cookies back to back with marmalade(or any fruit filling, thickened) in center and brush eggwhite mixture on outside, lightly brown, just a few minutes.