Peel the vegetables, and chop up roughly.
Put the vegetables and water in a pan, and bring to a boil. When it comes to a boil, turn down the heat to low and simmer for 30 minutes.
Let the boiled vegetables cool down, strain with a sieve, and it's finished.
Pour the soup into an ice cube tray, and freeze. You can defrost the cubes whenever you want. Cut the vegetables into shapes and mash to a consistency suitable for your child's age.