Put the diced potato and onions into a pan. Crumble over the stock cubes and pour over the cold water. Bring to the boil and then put the lid on the pan, reduce the heat to medium/low and simmer gently for 5 minutes.
Add the courgettes to the pan, season generously with salt and freshly ground black pepper, then put the lid back on and simmer for a further 10 minutes.
Remove the pan from the heat, sprinkle in the grated cheese and ground nutmeg and give it a stir. Leave to cool slightly and then use a stick blender to give it a good whizz.
To serve hot, return the pan to the heat and warm gently. Serve the soup in bowls garnished with a sprinkle of grated cheese and a little ground black pepper or nutmeg.
6 servings