Pork and Watercress Soup

Cut the pork ribs into pieces using the bone of the ribs as a guideline, if there is no ribs towards the end piece of the meat, cut into good size strips. Put this into a large pot and add water until it covers the meat, make sure that there is enough water for the soup, preferably 2-3 inches above the meat. Add a dash of salt and pepper. Wash the ginger and crush/smash whole then throw into soup. slice the onion so that there are in strips and add to soup along with the ginger. Heat should be set at medium to medium high. Cook for 25-30 minutes. In the meantime, soak the kombu in hot water. Peel potatoes and cut into quarters or smaller pieces, if desired. Do not cut potatoes too small. This will melt slightly and thicken soup. Leave this in a bowl of water so that the potatoes don't get brown. Take each kombu/seaweed strip (usually there are two to three strips per package) and tie knots into this, cut in between the knots and throw into soup. Cook for another 5-10 minutes before adding in potatoes. Continue cooking until potatoes are cooked or slightly melted (this can be tested by poking the largest piece of potato with a fork, if the fork can go thru the potato with easy then its ready). Turn heat down to low. Take watercress and wash well. Cut watercress into thirds or fourths. Add to soup and cover. Simmer for another 3-5 minutes or until the watercress is slightly melted. Add shoyu to taste and serve with rice.