Creamy French Watercress Soup

Prepare the potatoes by peeling and cutting them into small pieces.
Clean and prepare the leeks, cutting into ½ inch (1cm) lengths.
Chop the watercress finely after rinsing under running water.
Melt the butter in a heavy-bottomed pan large enough to hold all the ingredients.
Sauté leeks in butter until soft, 5-6 minutes.
Add the water or stock, potatoes, watercress, salt, and pepper to taste.
Cover and bring to a boil.
Reduce to medium-low and cook until potatoes are done, 10-12 minutes.
Blend in a liquidiser or blender, or use a stick blender in the pot.
Return to the pan if using blender, and add milk and cream slowly, stirring well.
Heat up without boiling, then reduce to simmer for a few minutes before serving.
Garnish with sprigs of fresh watercress and serve with croutons or your favourite bread.