Bread crostini (stale) with lentils (leftover)

Sauté the onion, add diced potatoes.
Separately, make a broth with potato, carrot, onion and celery.
Pour the vegetable broth over the sautéed onion and potatoes.
Add the leftover lentils and blend everything until you obtain a smooth cream. At this point, top the toasted stale bread with the cream.