Velouté de cresson

03 — Method

1. Wash the 2 large bunches of watercress in several changes of cold water to remove the grit hidden between the leaves. This is ESSENTIAL: watercress holds a lot of sand and tiny pebbles.
2. Pick the watercress, keeping the tender leaves and thin stems; discard the thick, fibrous stems. Set aside 1/4 for garnish.
3. Peel the 2 yellow onions and slice them thinly into even half-moons. Remove the green germ from the 3 garlic cloves and chop them with a paring knife. Peel the 400 g (14 oz) of potatoes and cut them into even 2 cm (¾ in) cubes so they cook evenly.
4. Melt the unsalted butter with 3 tbsp of olive oil in the large saucepan over medium heat without browning. Sweat the sliced onions for 8 minutes until translucent. Add the chopped garlic and cook for 1 minute, stirring, to release its aroma.
5. Add the potato cubes to the pot and cook 3 minutes, stirring. Pour in hot chicken stock to just cover. Season with fleur de sel and plenty of pepper halfway through cooking.
6. Bring to a simmer and cook 20 minutes over low heat until the potatoes are very tender. Add 3/4 of the watercress and cook just 3 minutes so it stays bright green.
7. Blend with an immersion blender right in the pot until perfectly smooth and bright green. If too thick, add a little hot milk.
8. Stir in the crème fraîche, the remaining milk and a pinch of grated nutmeg. Adjust the seasoning. Serve piping hot, topped with the reserved watercress, snipped chives and garlic croutons.