Pour the water and milk together in a saucepan and add the vegetable stock.
Peel the potatoes, onion and garlic cloves. Dice the potatoes, cut the onion into eighths and quarter the garlic cloves. Put the potatoes, onion and garlic in the saucepan and bring to a boil. Then simmer over low heat for about 15 minutes.
Meanwhile, cut the bread into cubes and fry them in a pan with the butter until crispy.
Then take the soup off the stove and puree it so that no whole pieces are left.
Just before serving, add the croutons to the soup.