How to make dashi: kombu, awase, vegan and instant

To make dashi, soak 10g of kombu in 1 litre of cold water for at least 30 minutes, heat it slowly and lift the kombu out just before the water boils. Then bring it to the boil, add 20g of katsuobushi (dried bonito flakes), turn off the heat, leave it for 2 to 3 minutes and strain. That gives you awase dashi, the clear, savoury stock behind miso soup and much of Japanese home cooking.

Dashi takes about 15 minutes of actual cooking and tastes far cleaner and more rounded than most instant versions. This guide covers the main types of dashi, including kombu dashi and a vegan dashi made with dried shiitake, when instant granules are good enough, what to use if you have no dashi at all, how to store it, and how to use up the kombu and bonito flakes afterwards.

What is dashi?

Dashi (出汁) is a light stock made by steeping ingredients rich in umami, the savoury taste, in water for a short time. Kombu, a type of dried kelp, is high in glutamate; katsuobushi, smoked and dried skipjack tuna shaved into flakes, is high in inosinate. Together they taste more savoury than either alone, which is why awase (combined) dashi is the everyday standard. Unlike a Western stock, dashi is never boiled for hours: long cooking makes kombu slimy and bonito bitter.

Types of dashi

Japanese cooks also talk about ichiban dashi (first dashi), the delicate stock from fresh kombu and bonito used for clear soups, and niban dashi (second dashi), a stronger, cloudier stock from simmering the same ingredients again. More on that below.

Recipe: awase dashi with kombu and katsuobushi

This is the dashi to make if you only learn one. It makes about 1 litre, enough for four to five bowls of miso soup or two bowls of noodle broth with some left over. Soaking the kombu overnight in the fridge gives the fullest flavour, but 30 minutes works.

Good dashi is clear and pale gold, smells gently of the sea and smoke, and tastes savoury rather than fishy. If it tastes of very little, the next batch needs a longer kombu soak or a few more bonito flakes; if it is bitter, the kombu was boiled or the flakes were squeezed.

How to make kombu dashi and vegan dashi

Kombu dashi is the simplest stock there is, and it is vegan. The easiest method is a cold brew: put 10g kombu in 1 litre of cold water in a jug or jar and leave it in the fridge overnight, or for at least 3 hours. Remove the kombu and the dashi is ready. You can also use the hot method from the recipe above and simply skip the bonito.

For a more savoury vegan dashi, add 3 or 4 dried shiitake mushrooms to the cold soak with the kombu and leave both overnight in the fridge. Shiitake release their flavour best when soaked slowly in cold water. Lift them out, squeeze them gently back into the dashi, and slice the softened mushrooms into the soup or a stir-fry. A combined kombu and shiitake dashi is the base of shojin ryori, Japanese Buddhist temple cooking.

Are instant dashi granules any good?

Yes, for everyday cooking. Instant dashi comes in a few forms, and most Japanese households keep one in the cupboard:

What can I use as a dashi substitute?

What to do with used kombu and katsuobushi

After making dashi, the kombu and bonito flakes still have plenty of flavour left. Don't throw them out:

How to use dashi

How to store dashi

Cool fresh dashi quickly, cover and keep it in the fridge for up to 3 days. It loses its aroma day by day, so it is at its best within 24 hours. To freeze, pour it into ice cube trays or small tubs and use within a month; a few cubes are handy for a single bowl of miso soup or a quick sauce. Keep dried kombu and katsuobushi in airtight packs in a cool, dry cupboard and use bonito flakes within a few weeks of opening, as they go stale.

Where to buy kombu and katsuobushi in the UK

Some supermarkets and health food shops sell kombu, but katsuobushi, dried shiitake, niboshi, dashi packs and instant granules are easiest to find at Japanese grocers and larger Asian supermarkets. Our directory lists 111 stores that stock Japanese groceries, and the cities with the most are London, Glasgow and Edinburgh.

Japanese specialists such as Japan Centre in central London and Kantenya in Brighton stock several grades of kombu and katsuobushi alongside instant dashi. Korean grocers sell dried kelp and dried anchovies for their own soup stocks, which work in much the same way. For everything else on a Japanese shopping list, see our Japanese grocery shopping guide.