Place 2 pounds of mustard greens in a bowl, add water, and mix. Sprinkle with 3 tablespoons of salt, ensuring the stems receive extra salt. Let sit for 2 hours, turning over every 30 minutes for even salting.
2
Thoroughly wash the mustard greens, paying special attention to soil and debris between the leaves. Rinse several times until clean, then drain and set aside.
3
Heat 0.5 cup of anchovy kelp stock and 1 tablespoon of glutinous rice flour over medium-high heat. Stir for about 2 minutes until bubbling begins, then add 1 tablespoon of sugar. Lower to medium heat and continue stirring.
4
Turn off the heat and add 0.25 cup of fish sauce. Allow the mixture to cool completely.
5
Stir 4 minced garlic cloves, 1 teaspoon minced ginger, 0.25 cup sliced onion, and 0.25 cup gochugaru into the cooled stock to create the kimchi paste.
6
Place the drained mustard greens in a container and add the paste, mixing thoroughly to coat all the leaves with the seasoning.
7
Place the kimchi in an airtight container or jar and refrigerate. Allow to ferment for around 2 weeks. For faster fermentation, leave on the kitchen counter for a few days until sour-smelling. Check daily and turn over occasionally to ensure the kimchi mixes well with the brine.