Heat a heavy soup pot over high heat, add the oil, and heat until hot, about 20 seconds. Add the tomatoes and scallions, and stir-fry until fragrant, about 15 seconds. Add the soy sauce and rice wine or sake, and stir-fry over high heat for 20 seconds. Add the water and salt, and bring to a boil. Reduce the heat to medium-low and cook for 2 minutes, skimming the surface to remove any impurities. Add the snow peas and stir.
Slowly add the cornstarch mixture and bring the liquid to a boil, stirring to prevent lumps from forming. Once slightly thickened, remove from the heat and slowly add the beaten eggs, pouring them in a thin stream around the edge of the pot. Carefully stir once or twice so that the eggs form thin streamers. Taste for seasoning and ladle into serving bowls.
Recipe courtesy of Nina Simonds