This isn’t really a recipe but rather “instructions for assembly”. The process is just as important as the ingredients, so I have put the critical steps in bold Italics.
Make a brine by dissolving 1 Cup of salt in a half-gallon of cold water in a large bowl. Yes, an entire cup of salt.
Stand one head of cabbage upright on its cut stem end, then cut vertically into quarters. Use a paring knife to remove the thick stem from each piece, then roughly slice the rest.
Transfer the cabbage into the bowl with the brine and stir it to soak. Let the cabbage sit for at least 4 hours or overnight at room temperature.
Drain the cabbage and rinse with fresh water, then use a salad spinner to dry.
In a food processor, combine 6 peeled cloves of garlic, 2 T. minced fresh ginger, and 3 T. thai fish sauce and puree roughly.
Clean 3 spring onions, then chop them up (greens and whites) and combine with the garlic mixture. Add 1-2 T. of your favorite chili paste.
Toss the spice mixture and 1 T. salt with the cabbage, making sure to coat the leaves as well as possible. You can also add 1 C. of shredded carrots, beets, or kale leaves.
Pack the kimchi into a half-gallon mason jar with a gasketed lid. Alternately, you can buy an airlock lid for use on a regular mason jar ($2 at most hardware stores).
Store the kimchi for 3 days in a cool place, but not in the fridge. After three days, keep it in the fridge until used. It will continue to ferment there. Use within three weeks for best flavor.