I've followed the recipe here to make a poppy seed filling. The filling ended up with a somewhat bitter aftertaste, and I am wondering the following: At what point of that recipe could something have happened to cause the bitterness? I tasted the seeds before and they weren't bitter, implying that something happened over the course of preparation. Could it have been something with the simmering (simmering too long, bringing it to a boil etc.)?