Miso soup from scratch: dashi, miso and timing

To make miso soup from scratch, first make a simple dashi. Soak kombu in cold water, heat it slowly, lift it out just before boiling, then steep bonito flakes for a minute or two and strain. Warm your tofu and wakame in the dashi, take the pan off the heat, and dissolve the miso in a ladle of the hot stock before stirring it back in. Don't let it boil after the miso goes in. That last step matters more than anything else in the recipe.

From start to finish it takes under an hour, most of it hands-off soaking. Here's how to get each part right.

What you need

For four bowls:

• 800 ml dashi (see below)
• About 60 g miso, adjusted to taste
• 200 g tofu, silken or firm, in 1.5 cm cubes
• 5 g dried wakame, soaked for 5 minutes and drained
• 2 spring onions, finely sliced

Step one: dashi

Dashi is the light, savoury stock at the base of much Japanese cooking. The classic version uses just two ingredients: kombu (dried kelp) and katsuobushi (dried, smoked bonito flakes). Kombu brings glutamate and bonito brings inosinate. Together they taste far more savoury than either does alone. This is the effect behind the word umami, coined by the Japanese chemist Kikunae Ikeda in the early twentieth century.

Classic dashi (makes about 1.2 litres)

1. Wipe 20 g of kombu with a dry or barely damp cloth. Don't wash it. The white powder on the surface is a natural savoury compound, not mould.
2. Soak it in 1.2 litres of cold water for at least 30 minutes, or up to a few hours. You can also leave it overnight in the fridge.
3. Heat slowly over low heat, taking about 15 minutes, until small bubbles form around the kombu.
4. Lift the kombu out just before the water boils. Kombu left in boiling water quickly turns slimy and bitter.
5. Bring to the boil, add 30 g of katsuobushi all at once and turn off the heat.
6. Let the flakes sink for a minute or two. Don't stir.
7. Strain through muslin or a fine sieve lined with kitchen paper. Let it drip, and don't squeeze the flakes, which makes the dashi cloudy and bitter.

Dashi keeps for about three days in the fridge and freezes well, so a double batch is worth making. For a plant-based version, soak kombu and dried shiitake in cold water overnight in the fridge. It's deeper and rounder than you might expect. The Art of Sushi gives full recipes for both Ichiban Dashi and Vegan Dashi. For more on stocks in general, see our guide to making stock from scratch.

What about instant dashi?

Dashi granules and powders are widely used in Japanese homes, and there's no shame in them on a busy evening. Follow the packet quantities and taste before adding the miso, because many are already salted. Homemade dashi tastes cleaner and lets you control the salt.

Step two: choosing your miso

Miso is a fermented paste made from soybeans, usually with rice or barley and salt. Styles vary enormously, but three broad types are easy to find:

Salt levels vary from brand to brand, so treat 60 g as a starting point. Add the miso gradually and taste as you go.

Step three: assembly and timing

This is where miso soup is made or ruined. Miso has a delicate aroma that fades with heat, so it goes in last, off the heat.

1. Heat the dashi to a bare simmer, no more.
2. Slip in the tofu and warm it through for about 2 minutes. Lower it in gently. Silken tofu breaks if dropped.
3. Add the drained wakame. Thirty seconds is enough.
4. Take the pan off the heat.
5. Dissolve the miso in a ladle. Hold a ladleful of hot dashi over the pan, put the miso in it and work it smooth with chopsticks or a small whisk, then stir it into the pan. Miso dropped straight in tends to clump.
6. Taste and add a little more miso if needed, dissolved the same way.
7. Serve at once in warmed bowls, scattered with spring onion.

If you need to reheat it, warm it gently and take it off the heat as soon as it's hot. Boiling flattens the aroma and can make the soup grainy.

Common mistakes

• Boiling after the miso goes in. The most common mistake by far. Heat gently and serve.
• Boiling the kombu. It turns the dashi slimy and bitter. Take it out just before the boil.
• Squeezing the bonito flakes. Tempting, but it clouds the stock and adds bitterness.
• Adding all the miso at once. Miso varies in saltiness, so add it in stages and taste.
• Making it far ahead. Miso soup separates and loses its aroma as it stands. Make what you'll eat.

Variations

Once you have the method, the fillings are yours to change. Clams steamed open in the dashi make a classic version. Aubergine works well in summer, and red miso gives you a heartier winter bowl. Mushrooms, thinly sliced daikon or fried tofu puffs are all traditional. For a fully plant-based soup, use kombu-and-shiitake dashi.

Miso soup is the natural partner to a sushi meal. The Miso Soup recipe in The Art of Sushi sits alongside other simple sides such as Agedashi Tofu, which also uses dashi. If you enjoy broths like this, our tour of soups of the world in 15 bowls is a good place to find the next one.

Questions people ask

Why shouldn't miso soup boil?

Boiling drives off miso's aroma, dulls its flavour and can make the soup grainy. If your miso is unpasteurised, strong heat will also kill its live cultures. Heat it gently and serve as soon as it's hot.

Can I make miso soup without bonito?

Yes. A dashi of kombu and dried shiitake, steeped cold overnight, gives a rich, fully plant-based stock. Check your miso's label if you're cooking for vegans.

How long does miso keep?

Miso keeps for a long time in the fridge once opened, and far longer than dashi. Its colour may darken over time. Follow the date on the packet.

Can I make the dashi ahead?

Yes. Dashi keeps for about three days in the fridge and freezes well, for example in ice-cube trays. Add the miso only when you're about to serve.