Prepare the Cabbage: Cut the napa cabbage in half, then soak in cold water and salt each leaf, focusing more on the stem part. Turn every 30 minutes for even salting, for a total of 2 hours.
Make the Porridge: Combine water and sweet rice flour in a pot. Cook until it starts boiling and thickens, then add brown sugar. Let it cool down completely.
Prepare the Vegetables: Cut the Korean radish into matchsticks and prepare the green onions. Optionally, prepare minari if available.
Make the Kimchi Paste: Puree garlic, ginger, and onion. Mix with fish sauce, fermented salted shrimp, and Korean hot pepper flakes to taste.
Wash the Cabbage: After salting, wash the cabbage thoroughly several times to remove excess salt.
Mix Kimchi Paste with Vegetables: Combine the radish, green onions, and optional minari with the kimchi paste.
Apply Paste to Cabbage: Spread the kimchi paste evenly between each leaf of the cabbage.
Ferment: Place the prepared cabbages into a Korean earthenware crock (Onggi) for fermentation.