In a medium-size saucepan over medium heat, please send the green onion and the liquid from the walnut pickle.

Bring it to a boil, and continue to simmer until it's reduced – approximately 10 to 15 minutes.

In another medium-sized saucepan over medium heat, place the pickled walnuts, soy sauce, mustard seed, chill powder, ginger, cayenne pepper and the anchovy.

Bring it to a boil and let it simmer for approximately 30 minutes.

When the green onion and the walnut pickle liquid have reduced, pour it into the other saucepan and stir well.

Continue simmering for another 15 minutes.

Turn off heat, let the mixture cool, before pouring it all into a closed glass jar.

Place in the fridge and let stand for several days.

Place a strainer over a bowl and press through the sauce, so only the liquid is left.