Clean, wash and cut the savoy cabbage into strips. Peel and chop the onions. Wash, halve and stone plums
Wash the duck breast and pat dry. Cut skin crosswise. Season meat. In a pan with no fat on the skin side, first fry vigorously for approx. 5 minutes, turn and continue frying briefly. Place the fillets in a flat ovenproof dish with the skin side facing upwards (keep the fat). Bake in a preheated oven (electric range: 200 °C/recirculating air: 175 °C/gas: level 3) for 15-20 minutes
Sauté half of the onions in hot frying fat. Deglaze with port wine and about 150 ml water. Stir in roast stock, bring to the boil. Simmer for about 10 minutes. Stir starch and 2 tbsp. water until smooth. Thicken sauce with it. Add the plums to the sauce and let them steep for about 5 minutes. Season to taste
In the meantime heat butter for the savoy cabbage. Fry the remaining onions in it. Add the savoy cabbage, season and sauté for about 5 minutes. Pour in just under 1/8 l water and bring to the boil. Steam everything covered for about 10 minutes. Season to taste with salt and pepper
Meanwhile cook the spaetzle in plenty of boiling salted water for about 12 minutes (or according to package instructions)
Roughly chop the almonds. Cut the meat open. Stir the resulting gravy into the sauce. Drain the spaetzle and arrange everything, sprinkle almonds over it