First, wash the spinach and cress, spin dry well and chop coarsely.
In a large enough pot, heat the butter and add the spinach and cress. Toss in it until the spinach collapses.
Add 1 liter of water and soup seasoning to taste, salt and pepper. Then stir in the whipped cream. Bring to a boil and simmer gently for about 20 minutes.
Blend the soup well before serving. Garnish with fresh cress leaves.