Peel and wash the carrots and potatoes and cut them into small cubes. Peel and finely dice the onion. Heat the fat in a pot and fry the onion in it. Dust with curry, steam briefly and stir in carrots and potatoes.
Pour in the stock, bring to the boil, cover and cook for about 15 minutes. Take out some vegetables with a skimmer and puree remaining vegetables in the stock. Warm the vegetables and shrimps in the hot soup and season with salt and pepper.
Serve with a dollop of sour cream. Dust with curry and serve garnished with chervil.