Heat the oil in a large non-stick saucepan and gently fry the onions for 6–8 minutes, or until softened and beginning to brown, stirring regularly.
Add the vegetable chunks and cook for 5 minutes more, stirring occasionally. Stir in the garlic and cook for a few seconds more.
Crumble over the stock cubes, add 1 litre/1¾ pints water and bring to the boil. Reduce the heat to a simmer, cover the pan loosely with a lid and cook for about 20 minutes or until the vegetables are very soft, stirring occasionally.
Remove the pan from the heat. Blitz the soup with a stick blender until very smooth and season with plenty of ground black pepper. Add a splash of just-boiled water if the soup is a little thick.
Ladle into bowls, top with freshly chopped parsley, if using, and serve with the bread.
