When you’re ready to cook the rabokki, put the pot of water, anchovies, and kelp on a burner set to medium-high and bring it to a boil. Simmer it for 10 minutes, then skim out the solids and keep simmering the clear broth for another 10 minutes.
“The amount of water used in this recipe makes for rabokki that isn’t too soupy or too dry,” Hoffman says, noting that you can reduce the water by up to ½ cup for a thicker sauce. For a soupier consistency, add ½ cup water.