For the zuppa di lenticchie boil the lentils with the whole peeled garlic cloves and the bacon cut into small cubes in about 1.5 l of water with a soup cube and salt for about 30 minutes.
Add the potatoes cut into pieces and cook on low heat for another 20 minutes.
Break the spaghetti into 3-4 cm long pieces and add to the soup. Let it simmer for about 15-20 minutes, adding a little more water if necessary.
Season the zuppa di lenticchie with pepper and salt, serve.