This is a Polish biscuit making technique which incorporates hard boiled egg yolks for a different flavour.
These cookies are pretty good, but they taste about the same as a butter cookie. However, these require some extra work, so I just suggest eating a butter cookie. They also have a weird texture...I suggest mixing the poppy seeds into the batter. - 04 Jun 2002 (Review from Allrecipes USA and Canada)
This is almost identical to the Polish Butter Cookie recipe that has been handed down in my family! The only major difference is we hard boil *all* of the eggs. To crumble to yolks, pushing them through a sieve works well. Also, we not only use poppy seeds, but any kind of sprinkles (red and green for christmas!) to top them. It has been a family favorite for many years! - 10 Dec 2006 (Review from Allrecipes USA and Canada)
THE COOKED EGG YOLKS ADD A GREAT TASTE SENSATION. WE ADDED THE POPPY SEEDS TO THE COOKIE DOUGH BEFORE BAKING AND THEY WERE MOIST AND SOFT FOR THESE OLD TEETH. IS NOW ONE OF MY FAVORITE COOKIES! - 06 Dec 2000 (Review from Allrecipes USA and Canada)