Whatever type of cookie dough you prefer, soft or crispy (I like the crispy type), if you make prune filling, take a jar of prune lekvar, add in some finely chopped walnuts, lemon juice, and allspice to taste (start off with a little juice and allspice at a time, and keep tasting until you love it). If you have no allspice, use cloves. These spices are very pungent and strong, so small doses are effective at flavoring something.
Anyone who has ever eaten our hamanatashen has not gone back to plain prune again.