In a saucepan heat the butter. Add the scallions, cover and simmer for 3 minutes or until soft. Add the broth and water and bring to a boil. Add the asparagus and simmer 5 minutes or until just tender. Add the peas and simmer 1 minute to heat through. Add the tofu or chicken, lettuce leaves and tarragon and simmer another couple of minutes or just until the romaine lettuce is wilted. Season well to taste with salt and pepper.