Mentsuyu substitutes

This is genuinely the answer, not a compromise, and it takes about five minutes. Combine, bring just to a simmer for two minutes to cook off the alcohol in the mirin, then cool for cold soba or use hot for kake udon. It tastes cleaner and less sweet than most bottled versions, which lean sugary. The same mixture at the dipping ratio is what tempura shops serve as tentsuyu, usually with grated daikon and ginger stirred in.

Best for

cold soba and somen, hot udon and soba, tempura dipping sauce, donburi, chilled tofu

A teaspoon of sugar per cup of finished sauce is the usual touch, but taste it. Bottled tsuyu is sweeter than most homemade versions, so add more if that is what you are used to.

The shortcut that makes this a genuinely weeknight job. Hondashi and similar granules give you the smoky bonito depth almost immediately. They do contain added salt and MSG, so the finished mentsuyu comes out saltier and a little more insistently savoury than one made with real kombu and bonito, and slightly less delicate. Cut the soy sauce by about a teaspoon per cup to compensate.

Best for

weeknight noodles, hot soba and udon broth, tempura dipping sauce, simmered dishes

Different brands vary a lot in salt. Make the dashi, taste it alone first, then decide how much soy sauce to add.

Soak a 4 inch piece of kombu and two dried shiitake in 2 cups of cold water for 30 minutes or overnight, then heat to just below a simmer and remove the kombu before it boils. The result is a clean, gently sweet, distinctly vegetal broth. Compared with bonito dashi it is noticeably less smoky and less animal, so the finished mentsuyu tastes rounder and slightly sweeter. Excellent, and the standard vegan approach.

Best for

vegan noodle broth, cold soba, vegetarian tempura sauce, hot pot dipping

Save the soaked shiitake and slice them into the noodles. If the kombu boils, the broth turns slimy and faintly bitter and cannot be fixed.

Ponzu is essentially mentsuyu's citrus cousin, made with yuzu or lemon juice alongside soy and dashi. Diluted it works, but the difference is unmissable: it is sharp, bright and acidic where mentsuyu is smooth and gently sweet. That makes it very good on cold soba on a hot day and wrong in a hot noodle soup, where the acidity tastes out of place and can turn a broth thin and sour.

Best for

cold soba, chilled somen, cold noodle salads, dipping sashimi-style

Add half a teaspoon of sugar or a teaspoon of mirin per cup to soften the acidity toward mentsuyu.

Worth being straight about: this is salty seasoned water and it tastes like it. You get the soy salinity and the sweetness, but none of the smoky, rounded dashi backbone that is the whole reason mentsuyu tastes the way it does, so the sauce reads flat and one-note. A pinch of MSG or a quarter teaspoon of fish sauce genuinely helps. It will get dinner on the table; it will not taste like a soba shop.

Best for

emergency substitution, hot udon broth, quick dipping sauce

If you have any dried mushroom, a piece of nori, or a few dried shrimp, steep one in the hot water for ten minutes first. Even that much makes a large difference.

If you do have a bottle, the real risk is using it neat. Most bottled tsuyu is sold as a 3x or 4x concentrate, and undiluted it is punishingly salty. Straight tsuyu, labelled hon-tsuyu or straight type, is ready to use for dipping and only needs thinning for soup. Getting the dilution right is the difference between a balanced sauce and an inedible one, so check the label rather than guessing.

Best for

soba and udon, tempura, donburi, simmered vegetables

As a rule, dipping sauce should taste slightly too strong when you sip it alone, because the noodles carry water. Soup broth should taste correct on its own.