Wash duck breasts, dab dry and season with salt and pepper. Heat oil in a pan and fry duck breasts on both sides over high heat. Then fry over medium heat for about 20 minutes, turning over.
Put the croquettes on a baking tray lined with baking paper. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 10 minutes, turning. Warm up apple-red cabbage at low heat for approx. 10 minutes, stirring occasionally.
Remove the duck breasts, wrap them in aluminium foil and let them rest for about 5 minutes. In the meantime peel and finely dice the shallots and garlic. Sauté in hot frying fat. Sprinkle with sugar, caramelise slightly and deglaze with Calvados.
Pour in the stock, bring to the boil. Wash thyme, dab dry, pluck leaves from the stems, chop finely and stir into the sauce. Stir in the sauce thickener, bring to the boil and simmer for about 2 minutes. Season apple-red cabbage and sauce with salt and pepper.
Cut open duck breasts, arrange on plates with croquettes, apple-red cabbage and sauce. Serve garnished with thyme.