A lot of Japanese dishes are quite subtly flavored to start with, and are eaten dipped in a simple soy sauce based dipping sauce. You’re probably familiar already with the wasabi + soy sauce combination used for most kinds of sashimi and sushi, but there are a few others. Which sauce goes with which dish really seems to depend as much on tradition as anything, though certain combinations just fit better than others. The ratio of flavoring to soy sauce is a matter of personal taste in most cases.
Whenever using a dipping sauce, try not to dunk whatever you are eating into it. The common sushi eating mistake made is to dunk the rice side into soy sauce - this not only makes the rice grains go all over the place, often down your front, but absorbs way too much soy sauce. Turn the sushi over and dip the fish just a bit instead. (I tend to think that this rice-dunking is why a lot of the finer sushi restaurants nowadays serve their sushi pre-seasoned, needing no dipping.)
Here are the most commonly used dipping sauce combinations:
- Wasabi (preferably fresh grated) + soy sauce (wasabi jo-yu) - used for most kinds of raw fish
- Grated ginger + soy sauce (sho-ga jo-yu) - used for “blue” or oily raw fish, such as mackerel, and bonito
- Grated garlic + soy sauce (ninniku jo-yu) - used sometimes for meat, and instead of ginger + soy sauce (my stepfather swears by garlic + soy sauce for bonito or even tuna sashimi)
- Reconstituted mustard powder + soy sauce (karashi jo-yu) - perhaps the most widely used combo; used for many things ranging from steamed pork buns to shuumai to meats. English mustard powder is the one to use, and never ever substitute pre-made French-style or other (hotdog-style) mustard. (In the movie Tampopo , as the gangster lies dying in his girlfriend’s arms, he tells her about hunting wild boar whose intestines are filled with yamaimo (Japanese yam) in winter, how good those intestines are and how he wishes he could have shared them with her. She sobs back to him, “they sound like they’d be great with mustard-soy sauce”.)
- Chili sesame oil (ra-yu) and soy sauce - the most popular dipping sauce for gyoza dumplings .
- Vinegar and soy sauce (su-jo-yu) - used for many things, to cut down on oiliness
- Citrus juice, most often yuzu and lemon, and soy sauce (ponzu) - used for many things. This is available bottled.
- Dashi stock, mirin and/or sake, sugar, and soy sauce (tsuyu) - this is the only sauce that’s heated after combining the ingredients, mainly to get rid of the alcohol in the mirin or sake and to melt the sugar. This is the standard dipping sauce for noodles, tempura and so on, and is used in different strengths depending on the usage. You can buy bottled concentrated tsuyu (often called mentsuyu, which means noodle sauce). The Japanese essence in a bottle is basically homemade concentrated tsuyu.