"This is an old Polish recipe from my grandmother that's been handed down a few generations. It's my absolute favorite cookie! There's something about the combination of the tart prunes and sugar that I can't quite describe; it's heavenly. I generally roll out the dough a little thicker than the original recipe calls for, making it chewier. If you like a crispier cookie, roll the dough thinner."
Mix flour with 1 lb margarine and salt, mix well. Add eggs, mix again.
On the stovetop, scald the milk then add vanilla. Pour in yeast to dilute. Allow to cool slightly.
Add milk/yeast/vanilla mixture to the dry ingredients. Knead dough until it comes clean away from the bowl.
Cover with waxed paper and chill for about 6 to 7 hours, allowing the yeast to rise.
When ready to make the cookies, mix 1/4 cup flour and 1/4 cup sugar together. Sprinkle on a board and roll out a small amount of dough. Cut into 3"x3" squares, place 1/2 tsp of prune filling in one corner and roll them.
Bake approximately 10 minutes for crispier cookies, 6-7 minutes for softer cookies.