Cream butter and sugars.
Add eggs, one at a time, and beat until light.
Add vinegar, vanilla, prunes, and sifted dry ingredients; mix well and add nuts.
Shape into 3 rolls about 2 inches in diameter.
Wrap in wax paper and chill overnight.
Cut into 1/8 inch slices and arrange on ungreased cookie sheets.
Bake in preheated hot oven (400°F.) for about 12 minutes.