Dice the potatoes and cook in boiling water until soft.
Roughly chop the cabbage and blanch it in the chicken stock for 10 minutes. Add the potatoes to the broth.
Heat the oil in a pan, add the leeks and garlic, simmer over low heat for about 5 minutes and add to the broth. Stir in the ginger, soy sauce and chili powder.
Season the soup with salt and pepper and serve hot.