Back when the Lower East Side was the Lower East Side -- a sweet-smelling stomping ground for immigrant culture and cuisine circa early 20th century -- everyone knew what a bialy was. Those who still know either speak Yiddish or have recently seen "The Producers" (Bialystock and Bloom). A bialy is flat, thin, garlicky, baked-hot and made from flour and dough. If not for its center filled with sweet onions, it's often mistaken for a bagel. You can still see the brick ovens where Kossar's (its full name is actually Kossar's Bialystoker Kuchen Bakery) has been famously making them since the 1920s. Strictly Kosher and closed on Shabbat, the dependable downtown shop for Sunday takeout also added "hand-rolled, kettle-boiled" bagels to their Atkins-defying roster -- which also includes bulkas, pletzels and sesame sticks -- with their cinnamon raisin and pumpernickel ranking as some of the oy-veyest in the city.