Halve the chicory lengthways, cut out the stalk, then cut the chicory into fine rings or pieces. Peel the potato and cut into small cubes. Finely chop the shallots.
Melt the butter in a saucepan over low heat, sweat the potatoes and shallots for about 3 minutes but do not brown. Put the chicory in the pot, sprinkle with sugar and curry powder and stir. Add the leek and pour the broth over it. Bring to the boil and simmer over low heat for about 30 minutes.
Puree the soup with the hand blender, add the cream and whip again. Season to taste with salt and pepper. Spread on plates and serve sprinkled with chives.