Prepare a pot, boil the water. Add tomatillos, onion, garlic and salt, simmer over low heat for 5 to 8 minutes. After slightly cooled, pour soup into a blender and puree. (Optional) You can add 2 or 3 raw tomatillos when you puree. They will make the color more greenish and give you a slightly different taste. Note: Increase the proportion of water to make soup. Add more tomatillos to make sauce and serve with tortilla or crackers.