Mustard greens kimchi (Gat-kimchi: 갓김치) recipe by Maangchi

Ingredients

• 2 pounds mustard greens
• 3 tablespoons kosher salt
• ½ cup anchovy kelp stock (or vegetable stock) or water
• 1 tablespoon glutinous rice flour (or rice flour, or plain flour)
• 1 tablespoon sugar
• ¼ cup fish sauce (or soy sauce)
• 4 cloves garlic, minced
• 1 teaspoon peeled ginger, minced
• ¼ cup sliced onion
• ¼ cup gochu-garu (Korean hot pepper flakes)