Trim the duck breasts and score the skin side with a sharp knife.
Press cracked peppercorns into the meat side and season with salt.
Place duck skin-side down in a pan over moderate heat for 5 minutes until crispy.
Turn the breasts and cook for 4 minutes more.
Remove duck from the pan and keep warm.
Discard excess fat and deglaze the pan with 50ml of cognac.
Stir in 100ml of stock and scrape up the caramelised juices.
Add 100ml of double cream and simmer until thickened.
Fry mushrooms in olive oil and 15ml of butter.
Sauté the spinach in the remaining 15ml of butter.
Combine the mushrooms and spinach.
Plate the mushroom mixture, top with sliced duck, and pour sauce around it.