Put the lentils in a colander and wash well.

Peel onions and cut them into fine pieces. Carrot, celery, clean and cut into fine cubes. Clean the leek well and cut into fine rings. Peel the potatoes and also dice them.

Heat the oil in a saucepan and sauté the onions until translucent.

Add tomato paste and fry briefly. Add the carrots, celery and lentils, stir briefly and then deglaze with the vegetable stock and bring to the boil.

Now add the leek, potatoes and bay leaf and simmer for 30 minutes with the lid closed. Stir occasionally.

Season the soup with salt, pepper and a dash of red wine vinegar.

Serve with chives rolls.