"Sauce." In Japan, this word refers to a rich, dark, bottled sauce sold in a number of varieties. Used on deep-fried foods like pork cutlets and Japanese croquettes, plus savory okonomiyaki pancakes, yakisoba noodles and more, this viscous sauce is an essential part of Japanese comfort cooking. But what is sauce made of? Even many Japanese people don't know! This time, we explore a sauce so essential, it's simply known as "sauce"!