Peel the onion. Dice approx. 3⁄4, cut the rest into strips. Heat butter. Sauté onion cubes briefly in it. Dust with flour, sweat briefly and deglaze with 1⁄2 l water, cream and cider. Bring to the boil, simmer for about 10 minutes. Stir in stock and season with salt and pepper.
In the meantime, cut the bacon into cubes and leave them crisp in a pan without fat. Take out and fry the onion rings in the bacon fat for about 5 minutes. Sprinkle with sugar and caramelise briefly. Deglaze with vinegar.
Wash the chives, shake dry and cut into small rolls. Wash the apple and dice the pulp. Puree soup and serve with apple, bacon, onions and chives.