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Recipe

Cold Tofu with Shio Koji: A 10-Minute Appetiser That Needs No Cooking

Cold tofu is one of the simplest dishes in the Japanese kitchen — silken tofu, straight from the refrigerator, dressed with something savoury. Shio koji replaces soy sauce as the dressing base here, adding enzymatic umami that plain salt cannot produce and soy sauce overcomplicates. The result is a dish that tastes considered despite requiring no cooking at all.

10-minute appetiser | 2 servings | no cooking required

Updated

IS THIS THE RIGHT RECIPE?

  • You have silken tofu and shio koji — make this recipe as written. The sauce takes 2 minutes.
  • You have shio koji but no tofu — see shio koji chicken or koji-marinated salmon for protein applications.
  • You want to understand shio koji first — read what is shio koji before cooking with it.
  • You want to make your own shio koji — follow how to make shio koji. It takes 7–10 days but only 15 minutes of active work.

What cold tofu with shio koji actually is

Hiyayakko — cold tofu — is a standard Japanese summer dish: a block of silken tofu served cold, dressed at the table. The canonical version uses soy sauce, grated ginger, and bonito flakes. This recipe replaces the soy sauce with a shio koji tare: a sauce built from shio koji, sesame oil, and rice vinegar.

The difference is not cosmetic. Shio koji contains active protease enzymes that break surface proteins into free amino acids — specifically glutamate, the compound responsible for umami. Soy sauce delivers umami through fermented soybean proteins; shio koji delivers it enzymatically, directly on the ingredient it touches. On silken tofu — which is nearly flavourless on its own — this produces a clean, layered savouriness without the colour or sharpness of soy. The dish tastes of tofu and something deeply savoury, not of soy sauce.

Myoga and katsuobushi (bonito flakes) complete the dish: myoga provides a floral crunch, and the bonito flakes bring smoky depth and visual movement as they flutter over the cold tofu.

Ingredients

  • 300g silken tofu (kinugoshi-dofu) — the softest grade. Chilled for at least 2 hours before serving, ideally overnight. Japanese silken tofu sold in aseptic cartons holds its shape better than water-packed varieties; either works. Do not use cotton tofu (momen-dofu) for this recipe — it is too dense and fibrous.
  • 1 tbsp shio koji — liquid (moromi-style) or paste. Liquid shio koji blends into the tare more smoothly; paste shio koji gives a slightly more textured dressing. Both are correct. If your shio koji is very salty (taste it — it should taste like well-seasoned rice, not pure salt), start with ¾ tbsp and adjust.
  • 1 tsp toasted sesame oil — this is a flavouring, not a cooking fat. Use the darkest, most aromatic sesame oil you can find. Chinese sesame oil (from toasted sesame) and Japanese sesame oil are interchangeable here.
  • ½ tsp unseasoned rice vinegar — brightness and balance. Do not substitute seasoned rice vinegar (it contains sugar and salt that will throw off the tare balance).
  • 1 myoga — sliced crosswise into thin rounds, about 1–2mm. Myoga is the flower bud of a Japanese ginger plant. It is delicate, slightly bitter, and floral — not hot like fresh ginger. Found in Japanese grocery stores; see the FAQ below for substitutes.
  • 3g katsuobushi (bonito flakes) — a small, loose handful. Katsuobushi adds smoky depth and, visually, moves in the heat rising from even a cold dish, which is part of the presentation.
  • Optional: 1 spring onion (green part only), thinly sliced. Adds colour and a mild allium sharpness if the dish feels too quiet.
  • Optional: a few drops of soy sauce to finish — if you want the familiar soy note alongside the shio koji umami. Keep it to 3–4 drops; this is accent, not base.

Instructions

1. Chill the tofu (2 hours ahead or overnight)

Place the sealed tofu block in the refrigerator for at least 2 hours before serving. The target temperature is 4–6°C — cold enough that the tofu feels firm to the touch through the packaging, and cold enough that the contrast between chilled silken protein and room-temperature tare is distinct on the palate.

If you are short on time: fill a bowl with water and ice, submerge the sealed tofu block, and leave it for 30 minutes. The tofu will cool to near-refrigerator temperature this way.

2. Make the shio koji tare

Combine in a small bowl: 1 tbsp shio koji, 1 tsp toasted sesame oil, ½ tsp rice vinegar. Stir until the shio koji dissolves into the oil and vinegar — it will not fully homogenise (shio koji is grainy), but it should be a cohesive mixture rather than separate components.

Taste the tare on its own. It should be assertively savoury — you are about to dress a large, mild block of silken tofu, so the tare needs to be seasoned to a level that feels slightly too intense in isolation. If it tastes flat, add more shio koji in ½ tsp increments. If it tastes only of oil, add a few more drops of vinegar.

This tare keeps for up to 3 days in the refrigerator. Make a double batch and use the remainder as a dressing for blanched vegetables or a dipping sauce for gyoza.

3. Drain and plate the tofu

Open the tofu package over the sink. If water-packed, drain completely. Tip the block gently onto a double layer of paper towel and blot the surface dry — you are removing free surface moisture so the tare adheres rather than beading up and running off.

Transfer to a serving plate. You can serve the block whole (the traditional hiyayakko presentation) or cut it into 4 equal slabs of approximately 75g each. To cut cleanly: use a sharp knife, wet the blade, and press straight down without dragging. Silken tofu tears if the knife drags sideways.

4. Dress, garnish, and serve

Spoon the shio koji tare evenly over the tofu — approximately 1 tsp per 75g slab, or distribute the full sauce quantity across the whole block. Scatter the myoga rounds across the surface. Pile the katsuobushi loosely on top so it sits airy rather than plastered flat. Add spring onion and the optional soy drops if using.

Serve within 3 minutes of plating. The tofu warms quickly at room temperature, the katsuobushi begins to wilt as it absorbs moisture, and the myoga loses its crispness. This is not a dish that holds.

Getting the shio koji ratio right

Shio koji varies considerably between brands and batches — salt content typically ranges from 5% to 13% by weight. This recipe is written for a mid-range shio koji of approximately 10% salt. If you are unsure of your shio koji's salinity, taste a small amount plain before starting:

  • Tastes like miso or lightly salted rice: use the full 1 tbsp as written.
  • Tastes aggressively salty: start with ¾ tbsp and add more after tasting the assembled tare.
  • Tastes very mild or sweet: use 1½ tbsp, or add a pinch of flaky salt alongside.

For full guidance on how shio koji behaves in different applications — marinades, sauces, quick pickles — see how to use shio koji.

Variations

Yuzu shio koji tofu. Add ½ tsp yuzu juice (or a small strip of yuzu zest, finely grated) to the tare. The citrus amplifies the rice vinegar's brightness and adds a floral note that works especially well in winter when yuzu is in season.

Shio koji tofu with shiso. Replace the myoga with 3 shiso leaves, cut into chiffonade. Shiso and shio koji share a clean, fresh-fermented quality that makes them natural partners. The dish becomes more aromatic and less crunchy — different texture profile, equally good.

Warmer-season version with cucumber. Add 3–4 thin slices of Japanese cucumber (or Persian cucumber) alongside the myoga. The cucumber adds water and crunch, making the dish feel more substantial as a summer starter. Salt the cucumber slices lightly (¼ tsp salt, 5 minutes), rinse, and pat dry before using.

Frequently Asked Questions

What does shio koji do to tofu?
Shio koji is a mixture of salt and rice koji (Aspergillus oryzae), and it does two things to tofu. First, its salt content seasons the tofu surface and draws a small amount of moisture to the surface, intensifying the flavour of the outer layer. Second, the protease enzymes in the koji break down surface proteins into amino acids — specifically glutamate — which is the biochemical source of umami. The result is tofu that tastes deeply savoury without tasting of soy sauce, and without the sharpness that plain salt would produce. This is why shio koji makes a more interesting dressing than soy sauce alone: it adds complexity through enzymatic activity, not just sodium.
Can I use firm tofu instead of silken?
You can, but the dish changes character significantly. Firm or extra-firm tofu (momen-dofu) has a denser, more fibrous texture and a stronger beany flavour. The shio koji tare works on firm tofu, but the silky, almost custard-like softness that makes this dish striking is gone. If you use firm tofu, consider pressing it for 20 minutes to remove excess moisture before plating, and increase the tare quantity slightly — the denser protein absorbs dressing less readily than silken tofu's wet surface. Firm tofu also holds up better for advance plating, if that matters for your situation.
What is myoga and can I substitute it?
Myoga (Zingiber mioga) is a Japanese ginger relative grown specifically for its flower buds and young shoots, not its rhizome. The buds have a mild, floral ginger flavour — far more delicate than fresh ginger root — with a slight bitterness and a crisp texture when raw. In cold tofu, myoga provides textural contrast (crunch against silken softness) and a bright, aromatic counterpoint to the umami-heavy shio koji. If myoga is unavailable, the best substitutes are: young ginger (very thinly sliced, used sparingly — it is hotter), thin-sliced spring onion whites, or a few shiso chiffonade ribbons. None of these replicate myoga exactly, but each adds the same structural role of a fresh, aromatic garnish.

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