Tsume Sauce is a sweet glaze used in old fashion Edo style sushi for cooked ingredients. The word tsume comes from nitsume orreduction. The tsume sauce is either made from the broth used to poach sea eel or hamaguri clams.
Tsume Sauce Ingredients:
For a cup of broth, use 1/3 cup of soy sauce, 2 tbs sugar and 1/5 cup of rice wine. Reduce the mixture to about a third until it becomes a syrup.
Fundamental in sushi and in the west you rarely find it. Foreign sushi chefs all over the globe use a sweetened sauce (bottled) to cover their toaster oven cooked frozen eel. Most foreign chefs use granulated or liquid instant substitutes found in Asian Markets, and its the sweetness that attracts most aficionados.