Dashi stock

• 1 x 5 cm piece kombu (dried kelp)
• 3 litres cold water
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Soak kombu in cold water for 1 hour, then drain. Wash snapper head thoroughly to remove all blood, then remove gills as they will make stock bitter. Put fish head into a stockpot with softened kombu, then add water and bring to a boil. Reduce heat and simmer gently for 30 minutes. Add bonito flakes and salt and simmer gently for 10 minutes. Strain stock through a fine-meshed sieve to remove all