How to Make It
In a medium saucepan, heat the butter over medium high heat until hot. Stir in the onion and cook until golden, about 5 minutes. Stir in the carrots, potatoes, stock and water and simmer, covered, until the carrots and potatoes are very tender, 15 to 20 minutes.
In a blender, puree the soup in batches, then stir in the cream and season with salt and pepper to taste. Serve drizzled with a little more cream.