Wash the fillets, pat dry and rub the meat side with marjoram and pepper.
First fry the fillets with the skin side down for 8-10 minutes in 1 tablespoon of oil. Turn, fry briefly on the meat side and season with salt and pepper. Fry for another 15-20 minutes over low to medium heat. Wrap in aluminum foil and let rest for about 5 minutes.
Deglaze the roast with the cognac, stock and cream. Add the peppercorns and poultry stock. Bring the sauce to the boil and simmer for approx. 5 minutes. Thicken the sauce and serve with the duck breast fillets.