Drain oysters and reserve the liquid. Mince oysters and place
in a saucepan. Add water and reserved liquid and bring to a boil.
Reduce heat, cover and simmer about 10 minutes. Remove from heat,
then add salt and cool completely.
Force the mixture through
a fine sieve into sauce pan. Measure the liquid, adding 2 tablespoons
light soy sauce to each 1/2 cup. Add dark soy sauce and bring to
boil.
Reduce heat and simmer gently for about 7 minutes.
Cool to room temperature and pour into a sterilized jar.