Peel the potatoes and dice them into 1cm / 0.5 inch cubes.
Heat a large pot over medium to medium high heat, melt the butter in it and add the chopped onions. Fry for 1-2 Minutes until translucent.
Add the potatoes and fry together for 2-3 minutes.
Add the white wine and chicken stock, turn down the temperature a bit, cover it and let everything cook for 15-18 minutes or until the potatoes are soft.
Meanwhile heat a small frying pan.
Add the bacon to it and let it gently fry until it has rendered its fat.
Add the bread and let everything fry until the croutons are crispy. Remove from pan and set aside.
When the potatoes are soft, remove 1 cup of the cooked potatoes from the broth and set aside.
Add the cream and crème fraîche to the pot and purée everything with a stick blender until creamy. If the soup is too thick add some more water. If it's too runny add some of the reserved potatoes and purée some more.
Add nutmeg and salt and pepper to taste. Return the reserved potatoes to the pot.
Before serving sprinkle the soup with the bacon/croutons mixture.