If using the starter culture, stir together the culture and water. Let the mixture sit while you prepare the other ingredients-around 10 minutes.
Remove and discard the outer leaves and core from the cabbage.
Shred the cabbage using a food processor or hand grater.
Combine the cabbage, carrots and radish in a large bowl.
Chop the green onions and add them to the bowl
Combine the garlic, ginger and fish sauce in a food processor or a blender and process until finely minced.
Add the garlic mixture, chili powder, and salt, to the vegetables mixture and toss gently but thoroughly to combine. You can also mix it with your hands, but if you do, wear rubber gloves to avoid chili burn.
Transfer the vegetables mixture to two 1 quart containers. Add your culture and then fill the containers with filtered water, leaving 2 inches of headspace to the let the veggies bubble and expand as they ferment.
Seal the containers and let them sit on your kitchen counter, out of direct sunlight for 3 days.
Check the vegetables every day to make sure they stay full submerged in water. If they have risen above the water, simply push them down so they are fully covered by the water.
When the veggies are done fermenting, place them in the refrigerator.
Sprinkle with sesame seeds before serving.