Drain 2 tablespoons of butter in a saucepan, sauté shallots, carrots and potatoes in it, add 1l of water, season with salt, pepper and broth and bring to the boil, cover and simmer for approx. 20 minutes.
Stir in the horseradish and puree with half of the cream in the food processor, season with salt and pepper
Fry the prawns in the remaining butter for 1 minute on each side.
Divide the soup on 4 plates, distribute the cream and make a pattern with a wooden skewer, serve 3 prawns on each.