Japanese kombu and bonito stock (Dashi)

1. Wipe the kombu with a dry, clean tea towel but don't wash it – the white coating is flavour.

2. Put it into a pan with the cold water and soak for at least 30 minutes.

3. Heat very slowly over medium-low heat; when tiny bubbles appear on the bottom of the pan (about 60-70 °C), remove the kombu – if it boils, it turns bitter and slimy.

4. Bring the water to the boil, turn off the heat and scatter in the katsuobushi.

5. Let the flakes sink on their own over 2-3 minutes.

6. Strain through a fine sieve or kitchen paper without squeezing the flakes; it keeps for 3 days in the fridge, or for months frozen.

Tip: Dashi is the soul of Japanese cooking: the base of miso soups, noodle soups and simmered dishes. Simmering the used kombu and katsuobushi again gives a milder "niban dashi" that's good for cooking.