Cover the potatoes with cold water and a little salt. Cook until soft.
Add the bread and rocket, taste, and add more salt if necessary. You may also need to add a little more water, in which case do make sure it is hot, not cold.
Heat the olive oil in a small saucepan and gently fry the chilli and garlic for a few minutes. Discard the chilli if you do not like it, and pour the oil and garlic over the soup.
Serve with freshly grated cheese.