Lightly sweat chopped shallots in hot butter. Deglaze with Noilly-Prat and pour in vegetable stock. Cut potatoes into small cubes, add with chopped garlic and let soup boil down vigorously for 20-30 minutes. Stir sour cream with some hot soup until smooth and mix in, but do not boil anymore. Season to taste with salt, nutmeg, white pepper and lemon juice. Stir in grated horseradish and blend with a hand blender. Meanwhile, dry the bread slices in the preheated oven at 120 °C until they are really crispy. Cut ham into small cubes and roast in a coated pan without fat until crispy. Serve foamed soup in preheated deep plates or bowls and sprinkle ham cubes on top. Place bread leaves decoratively and sprinkle with chopped chives.