Soupe de cresson

03 — Method

1. Wash the 2 large bunches of watercress several times in cold water — this is ABSOLUTELY essential, as watercress holds a lot of sand and grit.
2. Pick the tender green leaves and thin stems, discarding the thick, stringy stems. Set aside a quarter of the watercress to garnish.
3. Thinly slice the 2 yellow onions. Remove the germ from the 3 garlic cloves and chop them. Peel the 400 g (14 oz) of potatoes and cut into even 2 cm (¾ in) cubes.
4. Melt the unsalted butter in the large saucepan over medium heat and soften the onions for 8 minutes until translucent. Add the garlic and cook 1 minute, stirring, without browning.
5. Add the potatoes and stir for 3 minutes. Pour in hot chicken stock to cover. Season with fleur de sel and plenty of pepper halfway through.
6. Bring to a simmer and cook over low heat for 20 minutes until the potatoes are tender. Add three-quarters of the watercress and cook for just 3 minutes so it stays bright green.
7. Blend right in the pan with an immersion blender until perfectly smooth and bright green. If too thick, add a little hot milk.
8. Stir in the thick crème fraîche, the rest of the whole milk and the pinch of nutmeg. Adjust the seasoning. Serve piping hot topped with the reserved watercress, chopped chives and garlic croutons.