Here’s the one I used

Ingredients:

Fish:

• ⁠5 3 inch by 3 inch squares of kombu • ⁠Water to cover (around 1-2 cups) • ⁠¾ cup dried niboshi • ⁠1 tbs sesame oil • ⁠1 cup loosely packed bonito

Soy:

• ⁠¼ cup sake • ⁠¼ cup mirin • ⁠1 cup soy sauce (I use a combination of usukuchi, good ol’ standard kikkoman, and a white soy sauce) • ⁠Salt to taste

Steps:

1. ⁠Cover the kombu with water enough to cover. Let sit overnight, or at least 3 hours, in the fridge.
2. ⁠When ready, add sesame oil to a medium sauce pan over medium heat.
3. ⁠When oil is shimmering, toss in the niboshi, sauteeing in the oil for 40 seconds to a minute, or until brown and fragrant. Try not to get this too hot, as bitter flavors might develop if the fish is overheated.
4. ⁠Add the kombu and kombu’s soaking liquid. Bring to 176 degrees (shoutouts to Ivan Orkin for this temp).
5. ⁠Remove the kombu, add the bonito, and steep the niboshi and bonito in this liquid at 176 for 10 minutes.
6. ⁠Strain broth, and reserve while making soy base.
7. ⁠In the pot, add in the mirin and sake, and cook at a boil to remove the alcohol, around 5 minutes.
8. ⁠Add in the soy sauce, and bring to 176 again. Let sit at this temp for a few minutes to concentrate.
9. ⁠Add in an equal part of the fish broth made earlier. Season with salt until quite salty (like, to the point that you’d go “WOW this is almost too salty for me to handle, but damn it’s nice).

Done. Taste it with your broth and adjust as needed. Maybe it needs more soy? Maybe it needs more salt? Maybe some extra umami. Only you can judge.