To Make Katsuobushi/Kombu Dashi:

1. Break the kombu into a couple of pieces and then soak the kombu in the water for at least 1 hour (or even overnight) in the fridge.*
2. Pour the kelp water into a pot (save the kombu for a different purpose) and bring to a simmer over medium heat.
3. As soon as the liquid starts to simmer, add the katsuobushi and turn off the heat. Let the liquid steep for 15 minutes.
4. Strain the dashi through a sieve and then use the stock immediately or transfer to the fridge or freeze. The stock keeps for 5 days in the fridge. 

To Make Anchovy and Kombu Dashi:

1. Break the kombu into a couple of smaller pieces. Add it to the water and soak the kombu for at least 1 hour or overnight in the fridge. 
2. Head and gut the sardines by breaking off the heads and then pinching out the guts which are hard and black. Discard the head and guts.
3. Pull the kombu out and reserve for another use. Then put the anchovies in a pot with the soaking water. 
4. Bring the pot to a simmer over high heat. Partially cover the pot with a lid, lower the heat to medium and continue to simmer for 15 mins and then strain out the sardines. Either discard or use the sardines in another dish (if you have pets, they love the cooked sardines). 
5. Use the stock immediately or transfer to the fridge or freeze. The stock keeps for 5 days in the fridge. You can substitute 2 cups of katsuobushi (about 2 cups or 20 grams for the iriko)

To Make Vegetarian Shiitake Mushroom and Kombu Dashi:

1. Break the kombu into a couple of smaller pieces. Put the kombu in a container with the water. Wipe off the mushrooms and then soak the mushrooms with the kombu. You can put a bowl on top of the mushrooms to keep them submerged. Soak for at least an hour or even overnight. 
2. Strain out the kombu and then put the mushrooms and soaking water in a pot. Bring the pot to a bare simmer and then turn off the heat. Let the mushrooms sit in the cooling pot for 10 minutes. 
3. Squeeze the mushrooms to extract as much liquid as you can and reserve the mushrooms for another purpose. Use immediately or transfer to the fridge or freeze. The stock keeps for 5 days in the fridge.