Add the lentils, tomatoes, mushroom water and bay leaf to the pan and cook over a medium heat for 30 minutes until the lentils are soft but not yet falling apart.
Preheat the oven. Dice the bread and drizzle with the remaining olive oil. Then spread on a baking tray lined with baking paper and toast in the hot oven until golden brown.
Grate the parmesan.
Season the finished soup with salt if necessary. Finally, arrange on plates and serve sprinkled with the white bread croutons and grated Parmesan.