Clams and Prawns with Tausi Recipe

1 tablespoon cooking oil

1/2 cup onions, chopped

1 tablespoon ginger, chopped

4 tablespoons canned salted black beans (tausi)

1/4 cup green onions, chopped

1/4 cup parsley, finely chopped (optional)

1 cup water

1 kilo manila clams, or halaan, cleaned

1/3 kilo prawns, cleaned

salt, to taste