I tried a Halva (gound sesame and sugar kind of sesame marzipan) of a kind I didn't try before, and I find it smells like Play-dough. My wife says that when she makes Play-dough from flour it also has the 'Play-dough' smell. Could there be a common ingredient to the two? Maybe cream of tartar? Thanks!
Are you sure it was a sesame based Halva? Halva generally falls in to two wide varieties, one flour based and the other nut based. I would assume that the smell of play-dough comes from the flour. So it's possible you had a flour based one.
BTW, it's wikipedia that's defining Tahini as being nut based, I'm not so sure about that classification myself.