Pour in 2L (8.5 cups) of water into a large pot. Carefully clean-out 20 Large Dried Anchovies - by splitting them with your fingers and removing the black innards. Add the 20 cleaned anchovies into the pot. Then add a hand-sized piece of Dashima into the pot as well. Next, add a stalk of Spring Onion. (Alternatively, you can simply use 2 anchovy-kelp broth bags). Place on high heat and bring up to boil.
Once it starts to boil, set a timer for 10 minutes. After 10 minutes, turn off the heat. Take out the anchovy, kelp pieces and the spring onion stalk - throw them out. Then use a soup ladle to skim-off any residual bubbles that float on top of the broth.
Then scoop out 3 soup ladles of the broth into a small bowl. Set this small amount of broth aside for now - we'll use it in later steps when making the dipping sauce.
Transfer the stock broth into a pot you will use for hot pot. If your pot can't fit all of the broth - no worries! Just fit as much as you can - you can add more broth later.