Was ist das für eine Soße?

looks like 새우젓

https://youtube.com/shorts/-39gfLzkaGk

Meljeot is a Jeju style fermented anchovie sauce.

멜젓소스 (meljeot sauce, Korean salted anchovy sauce)

https://youtu.be/_V_i0WnFtuc?si=SHFc8kg8ZUhD7EdR

Getting Korean whole salted fermented anchovies will be the hard part, since that cannot be substituted

fermented anchovie sauce with some soy paste (된장), garlic and chopped peppers.
I think you need to put some water there as well, to make it a bit soupy as shown in the photo.
I don’t think anchovie sauce (멜젓) is absolute must ingredient, as it can be replaced with other fish sauce, and it is hard to get if you are out of Jeju i think.