Put first nine ingredients in a sauce pan. Bring to boil and simmer covered 10 minutes Add shrimp and tofu and cook until shrimp is done (about 3 minutes). Stir water into cornstarch. Stir into soup. Slowly add the egg in a thin stream, stirring gently. Continue cooking soup until it thickens slightly and is bubbly. Remove from heat and add coriander. (If fresh coriander isn't available, use parsley and about 1/8 t ground coriander.)