2 tbsp olive oil
1 small onion, chopped
600 g potatoes, diced
300 g watercress, chopped
100 ml water
1 litre chicken or vegetable stock
freshly ground black pepper
a pinch of freshly grated nutmeg
1. Heat the olive oil in a saucepan and cook the onion and potato over a medium-low heat for 20 minutes. Add the watercress (keep a little back to use for garnish) and water and cook for 5 minutes until the watercress wilts.
2. Add the stock, seasoning and nutmeg, bring to the boil and gently simmer for 15 minutes.
3. Blend with a hand-held blender until smooth. Check the seasoning, scatter with the reserved watercress and serve at once.