Dashi: the quiet stock behind almost everything

If you have ever tasted a Japanese clear soup and wondered how something so pale could taste so full, the answer is almost always dashi (出汁). It looks like weak tea. It smells faintly of the sea and of a distant woodsmoke fire. And it holds up a startling share of Japanese cooking, from the bowl of miso soup at breakfast to the broth under a bowl of udon.

What I love about dashi is how little it asks. There is no roasting of bones, no all-day simmer, no endless skimming. You steep a couple of dried ingredients in water, briefly and gently, and pour off something that tastes far bigger than it has any right to.

Two ingredients, one big idea

The classic dashi is made from kombu (昆布), a thick dried kelp, and katsuobushi (鰹節), skipjack tuna that has been simmered, smoked and dried until it is as hard as wood, then shaved into flakes. Each brings its own savoury compound. Kombu is rich in glutamate; katsuobushi is rich in inosinate.

Both are carriers of umami, the meaty, mouth-filling "fifth taste" that a Japanese chemist first put a name to after studying, of all things, kelp broth. That story deserves its own telling, and it has one in the discovery of umami.

The clever part is what happens when the two meet. Glutamate and inosinate amplify each other, so a stock made with both tastes far more savoury than you would expect from simply adding their effects together. Food scientists call this umami synergy. Japanese cooks found it the practical way, long before anyone measured it, and it goes a long way to explaining why kombu and katsuobushi became the classic couple.

It also explains why good dashi tastes complete without much salt. The umami does a lot of the work that salt and fat would do elsewhere, which is one reason a dashi-based soup can feel rich while staying light.

First dashi, second dashi

Japanese kitchens traditionally make dashi in two rounds.

Ichiban dashi (一番だし), "first dashi", is the delicate one. The kombu goes into cold water and is warmed slowly, then lifted out just before the water boils. The katsuobushi flakes go in, steep for a minute or two, and the stock is strained without pressing the flakes. The result is clear, pale gold and perfumed. This is the dashi for clear soups like suimono, where there is nowhere for a flaw to hide.

Niban dashi (二番だし), "second dashi", is made by simmering the same kombu and flakes again in fresh water, often with a few extra flakes added. It is cloudier and less fragrant, but sturdier. That makes it ideal for simmered dishes, for miso soup, and anywhere other strong flavours will join the party.

I find something quietly admirable in this two-step habit. Nothing goes to waste, and each extraction has its own job.

One rule matters more than any other: do not boil the kombu hard. Kelp that is boiled aggressively can make the stock slimy and bring out bitter, overly marine notes. Soak it, warm it, and take it out before things get rowdy. There is more on why in our piece on kombu.

The wider dashi family

Kombu and katsuobushi are the famous pair, but they are far from the only way to make dashi.

• Niboshi dashi uses niboshi (煮干し), small sardines or anchovies that have been boiled and dried. It is bolder, a little bitter and wonderfully homely. It is also the backbone of many ramen broths; you can search the map for niboshi shops to see how far that idea has travelled.
• Shiitake dashi comes from soaking dried shiitake mushrooms. They contribute guanylate, a third umami compound, which also teams up well with glutamate. The result is earthy, dark and lovely in simmered vegetables.
• Kombu dashi on its own is a base of much Buddhist temple cooking, shojin ryori (精進料理), which avoids fish and meat. It is soft and gently sweet, and easy to make: some cooks simply leave a piece of kombu in a jug of cold water in the fridge overnight.

In everyday homes, plenty of people use instant dashi granules or tea-bag-style dashi packs. I don't think that is anything to be snobbish about. They put the flavour within reach on a busy weeknight, and making the real thing once in a while is the best way to understand what those packets are imitating.

Tasting dashi, wherever you find it

Once you know the taste, you start noticing dashi everywhere in Japan. It is the base of the broth in a bowl of soba or udon, the liquid in a pot of oden, the soul of miso soup. Many ramen shops blend a seafood stock built on the same ingredients into their pork or chicken soup.

If you want to really taste it, order something where dashi does most of the talking: a clear soup with a set meal, or a simple bowl of kake udon or kake soba, plain noodles in hot broth. Take the first sip before you add anything. Notice the faintly smoky edge from the katsuobushi, then the round, lingering savouriness underneath that comes from the kombu.

It is a strange thing to fall for a stock that is mostly water. But dashi teaches a lesson that runs through Japanese food as a whole: the deepest flavours are often the ones that do not shout.