Heat the butter in a pan, add the onions and sauté a little, add the apples and continue to cook, add the red cabbage, season a little with salt and sauté well. Add the jam, continue steaming. Add the flour, mix everything well and lightly roast, while stirring, deglaze with the cold vegetable stock. Then let the whole thing boil, half covered, over low heat (approx. 45 minutes).
Mix the cream and egg yolk together, add to the soup and puree everything very well with the hand blender. Season to taste with salt, pepper and a little cinnamon.
Sprinkle with a little chives to serve and serve immediately.