The flavor of the chicken stock for this soup is boosted by cooking it with the empty pea pods and scallion greens.
In a large saucepan, combine the chicken stock with the water, pea pods, scallion greens and ginger. Cover and simmer over low heat until the stock is flavorful, about 10 minutes, then strain, pressing on the solids to extract as much liquid as possible; discard the solids.
Return the stock to the saucepan, season with salt and bring to a simmer. Add the English peas and cook over moderately high heat until tender, about 7 minutes. Add the sugar snaps and snow peas and cook until crisp-tender and bright green, about 1 minute. Add the tofu and cook just until heated through, about 30 seconds. Remove the pan from the heat and stir in the sliced scallions, cilantro and vinegar. Season with salt and pepper. Ladle the soup into bowls and serve.
Wine Recommendation: Match the attractive "green" flavors of this soup with an herbal California Sauvignon Blanc, such as the 1997 Markham or the 1997 St. Supéry.