Like so many Yiddish words, schmaltz has mixed connotations - it can be used to describe something fine and expensive or something corny and over-the-top sentimental. But for many cooks, its true meaning lies on the palate. "If you don't use schmaltz, your food will be flavorless," says Russ Farer, general manager at Schlesinger's Deli in Center City. "It's that simple."