Peel and roughly dice the onion. Clean or peel and wash leek and carrots. Cut the vegetables into long thin strips. Wash duck breast and pat dry. Cut the skin crosswise
Heat a flat roaster or an ovenproof pan on the stove without fat. Season duck breast with salt and pepper. Only on the skin side, fry vigorously for 4-5 minutes. Then turn and fry over medium heat for 2-3 minutes. Spread the onion around the duck breast and roast in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for 20-30 minutes
Roast sesame seeds in a pan or pot without fat, remove. Heat oil in it. Season vegetables with salt and pepper. Steam covered for 5-7 minutes.
Remove the duck breast and keep it warm. Skim plenty of duck fat, remove onion. Dissolve roast with 200 ml water. Stir in vinegar and stock. Bring everything to the boil, then boil down for 1-2 minutes over high heat. Bind with sauce thickener and season to taste. Swivel vegetables in the sauce
Arrange duck breast with balsamic vegetables. Sprinkle with sesame seeds and garnish with basil. Serve with golden brown croquettes