Peel and halve onions and cut half into cubes, the rest into rings. Heat the oil in a pot. Fry the onion cubes in it for about 15 minutes at medium heat, stirring occasionally.
Dust with sugar and flour, sweat briefly, deglaze with stock, cream and cider. Bring to the boil, simmer gently for about 15 minutes. Season to taste with salt and pepper.
Heat the fat in a frying pan, stir-fry the onion rings for approx. 5 minutes, sprinkle with sugar and allow to caramelize. Deglaze with vinegar, let it boil down slightly for about 1 minute, season with salt and pepper.
Wash the chives, shake dry and cut into fine rolls. Apple wash, quarter, remove core and cut quarters into cubes. Cut bacon into cubes and leave to crisp in a pan without fat, remove and drain. Arrange soup in a bowl, add apple, bacon and caramelized onions. Sprinkle with chives.