Chef Heidi Rae Weinstein holds a Reuben sandwich, complete with Swiss cheese — definitely a kosher no-no — at Trefa Banquet 2.0, an event held in San Francisco to commemorate a scandalous meal held in 1883 by newly ordained rabbis of the Jewish reform movement. The event has practically become myth. Lydia Daniller hide caption

Boxes of "Surprisingly Delicious Matzo" made by The Matzo Project line the shelves of Glen's Garden Market in Washington, D.C. Kelly Jo Smart/NPR hide caption

A Passover Seder table. During Passover, Jews avoid leavened bread. But whether legumes, corn and rice are OK has long been a point of contention among Jews of European and Middle Eastern ancestry. Now, rabbis have weighed in. Reza/Getty Images hide caption

University of Illinois student Stanley Dayan (from left) and Chabad Jewish Center employees Mordy Kurtz and Yosef Peysin work at the center's kosher food stand in 2013 at the university's State Farm Center basketball arena in Champaign, Ill. David Mercer/AP hide caption

The holes in matzo give the cracker its characteristic crunch, Odelia Cohen/iStockphoto hide caption

Ritually slaughtered lamb is delivered at a halal butcher shop in The Hague, Netherlands, in 2011. Denmark, Sweden and Norway are among the countries requiring animals to be stunned before slaughter. Dutch lawmakers took up the issue in 2012. Peter Dejong/AP hide caption

What's what? In Israel, the shape of a boureka pastry traditionally tells you what's inside. Now the country's chief rabbis want the shapes to get a lot more specific to help people keep kosher. Emily Harris/NPR hide caption

Israelis eat at a kosher McDonald's restaurant in Tel Aviv. David Silverman/Getty Images hide caption

This matzo ball soup may be kosher, but that doesn't necessarily mean it's better for you. iStockphoto.com hide caption