First, clean the leeks and cut into rings. Peel and coarsely dice the potatoes.
Place both in an unperforated cooking container with the vegetable soup and cook (at 100 °C for 16 minutes or at 120 °C for 8 minutes).
Puree soup and season with salt and pepper. Stir in cream and heat (at 95 °C for 2 minutes).
Chop the herbs, pour over the potato soup and serve.