Place 2 litres cold water in a saucepan and add 2 x 10 cm squares of dried kelp with a 1 cm fringe, previously wiped with a damp cloth. Bring almost to the boil and remove the kelp, bring to boiling point, add 12 g bonito flakes and remove from the heat. Allow to stand for 3 minutes, strain and use as required. The kelp and bonito flakes should be kept for making Second Soup Stock.