Cover the lentils with 1.5l of water in a large pot and boil for about 30 minutes or until the lentils are very tender, skimming off any foam.
Add the spice mix, cumin, salt and verjuice, and cook for 10 minutes, until the lentils have broken down. In a separate pan, heat the olive oil and saute the garlic until golden brown.
Pour into the soup, mix well and cook for two minutes. Garnish with croutons, if using, and pepper.