In a skillet cook the bacon over moderate heat, turning it, until it is crisp, transfer it to paper towels to drain, and crumble it. Transfer 1 tablespoon of the fat to a heavy saucepan and in it cook the onion over moderately low heat, stirring, until it is softened. Add the broth, 1 cup water, and the lima beans, simmer the mixture for 8 minutes, or until the beans are tender, and season it with salt and pepper. In a food processor purée the soup, return it to the pan, and heat it over moderate heat until it is hot. Ladle the soup into 2 bowls and sprinkle the scallion green and the bacon over it.
