Chop 3 onions and fry off with a small splosh of olive oil in a large saucepan for 5ish minutes. Add 3 large potatoes, chopped (should be around 780g) and cook, covered for another 5 minutes. Chop the two 85g packs of watercress, and add with a litre of vegetable stock. Bring to the boil and cook until the potatoes are tender, which should take about 15 minutes.

Blend the mixture, while adding 500ml of semi-skimmed milk, a freshly grated nutmeg and some black pepper. Reheat to serve.