Cut the cabbages lengthwise in half, then cut a short slit at the base of each half. Gently pull the halves apart to split them into quarters. This preserves the leaves.

Dunk the cabbage quarters in a large basin of water to get them wet. Sprinkle the coarse sea salt between the leaves, concentrating more salt near the thicker stem ends. Let rest in a basin for 2 hours, turning them over every 30 minutes to ensure even salting.

Rinse the salted cabbage quarters thoroughly in cold water 3 times to remove excess salt. Drain them cut-side down in a colander for at least 30 minutes to remove as much water as possible.

While the cabbage drains, make the sweet rice porridge. In a small saucepan, whisk together 2 cups of water and 2 tablespoons of sweet rice flour. Bring to a boil over medium heat, stirring constantly until bubbles form and the mixture thickens slightly. Stir in the sugar, cook for 1 more minute until translucent, then remove from heat and let cool completely.

In a food processor or blender, combine the garlic, ginger, onion, Asian pear, fish sauce, and salted shrimp. Blend until smooth.

In a large mixing bowl, combine the cooled sweet rice porridge, the blended garlic-ginger mixture, and the gochugaru. Stir well to form a thick, vibrant red paste. Fold in the julienned radish and scallions.

Put on food-safe gloves. Take a quarter of the drained cabbage and rub the paste generously over every leaf, starting from the outside and working in, concentrating more paste on the thicker stem ends. Fold the quarter in half and pack it tightly into a clean glass jar or kimchi container.

Leave about 1.5 to 2 inches of headspace at the top of the jar to allow for expansion during fermentation. Close the lid tightly.

Leave the jar at room temperature (out of direct sunlight) for 1 to 2 days to kickstart fermentation. You will see bubbles forming and juices rising. Once it smells sour and tastes ripe to your liking, move it to the refrigerator to slow down fermentation.