On a recent trip to Sadelle’s, a modern Jewish deli in the SoHo neighborhood of Manhattan, I got a sudden craving for a bialy. As I ogled bagels, stacked and Instagram-ready on wooden dowels, I asked the hostess with gleeful anticipation if they had my favorite Jewish bread. My question was met with a blank stare.

“A what?” she asked.

“A bialy,” I replied.

“What’s that?”

Oy, I thought.

To be fair, nowhere is it written that a Jewish deli is obligated to sell bialys, much less know what they are. But I’m someone who laments the dearth of good bialys in the world, and I worry about their survival.

First things first: a bialy is ...