For the must soup, finely chop the spring onions and slice the peeled potatoes and leeks.
Melt the butter in a saucepan, add the onions, fry until light and dust with flour. Roast everything briefly and pour in must. Add soup and bring to a boil.
Mix in prepared vegetables and cook for about 10 minutes. Stir in crème fraîche and let the soup boil down again until creamy. Season to taste with salt, freshly ground pepper and nutmeg.
Meanwhile, in a small frying pan, brown the diced smoked meat in a little melted butter. Serve the hot soup on warmed soup plates and sprinkle with the freshly chopped herbs and the diced smoked meat before serving.