Peel 3 onions and cut into slices. Wash the legs, possibly clean and shine them. Put the legs, half the onions, 2 bay leaves and peppercorns in a pot, cover with water.
Bring to the boil, cover and simmer over medium heat for about 45 minutes. In the meantime clean, wash and cut leek into rings. Peel, wash and cut carrots into pieces. Take the legs out of the pot, dab dry with kitchen paper and season with salt.
Place on the fat pan of the oven. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 50 minutes. Measure 400 ml duck stock. Pour 100 ml stock onto the fat pan after approx. 30 minutes.
Heat 2 tablespoons of oil in a frying pan, fry the remaining onion slices, leek and carrots while turning them. Add 300 ml duck stock and duck stock, bring to the boil and simmer for about 20 minutes. Pour into a sieve, drain well and collect the stock.
Peel and finely dice 1 onion. Heat clarified butter in a pot and fry onion. Add red cabbage, cloves, 2 bay leaves and 200 g apple compote, bring to the boil and braise for about 10 minutes.
Heat 1-2 tablespoons of oil in a large frying pan. Spread out deep-frozen croquettes in the pan. Bake at medium heat according to the desired degree of browning, shaking the pan several times. Wash the thyme, shake dry and pluck the leaves from the stalks.
Remove the fat pan from the oven, take the legs of duck off and keep them warm. Pour the stock onto the fat pan. Loosen the frying pan and pour into a pot. Bring to the boil, stir in sauce thickener, bring to the boil again and season with salt, pepper and sugar.
Arrange duck legs, red cabbage, croquettes and sauce on plates, sprinkle with thyme. Add the rest of the apple compote.