Step 1

Add the cold water in a large Dutch oven.

Step 2

Add the kombu seaweed.

Step 3

Heat over medium heat without boiling then lower the temperature, cover and maintain the temperature at 150 F (65 C) for 1 hour over a very low heat.

Step 4

Add the bonito flakes into the broth and raise the temperature to about 185 F (85 C) without boiling.

Step 5

As soon as the bonito flakes go down completely to the bottom of the pot, about 4 minutes, remove from heat.

Step 6

Filter the broth.

Step 7

Let cool completely.