Watercress soup

For 4 people as a starter, for 2 as a main course

• 250g (8 oz) of watercress
• 2 medium potatoes
  (about 250g) (8 oz)
• 1 stock cube
• 1 piece of butter
• 1 onion
• heavy cream
• salt, pepper

Cook the peeled and cut into pieces potatoes in boiling water with the stock cube.

In a large frying pan, stir the chopped onions in butter or vegetable oil, then sweat the watercress.

When the potatoes are done, add the watercress and mix everything with a knob of butter. Salt and pepper.

Serve with a spoonful of heavy cream.