Shorten the watercress stems a little. Read out the watercress, wash and drain. Pluck some cress leaves from the stems and put aside for garnishing, chop the rest. Peel and finely chop the onion.
Heat 1 tablespoon of butter in a saucepan. Sauté the onion in it. Dust with flour, briefly
Sweat until golden yellow. Add 400 ml water while stirring. Stir in stock, bring to the boil, simmer for about 5 minutes
In the meantime cut the bread into small lozenges or cubes. Heat 1 tbsp. butter in a pan and toast bread in it while turning. Season with a little paprika and take out.
Add half the crème fraîche and chopped watercress to the soup and blend briefly with a hand blender. Season with salt, pepper and 1 pinch of sugar. Fill into small bowls, add the rest of the crème fraiche.
Sprinkle with cress leaves and croutons.