- With the rack in the middle position, preheat the oven to 190°C (375°F).
- Using a sharp knife, score the skin of the duck breasts in a large crosshatch pattern, exposing the fat but not cutting into the meat.
- In an ovenproof non-stick skillet over low heat, brown the breasts skin side down for about 15 minutes, spooning off and saving the fat as it is rendered. Season the breasts with salt and pepper. Turn the breasts, raise the heat to medium and cook for about 2 minutes. Transfer the breasts to a plate.
- In the same skillet over medium-high heat, brown the radicchio on all sides in 45 ml (3 tablespoons) of the reserved duck fat. Season with salt and pepper. Add the apples and continue cooking for about 2 minutes. Add the broth and maple syrup. Bring to a boil. Place the duck breasts on top, skin side up, and transfer to the oven. Roast until medium-rare, about 7 minutes. Transfer the breasts and radicchio to a warm plate, cover loosely with aluminum foil and let rest 5 minutes.
- Just before serving, add the butter to the apples, stirring with a wooden spoon. Adjust the seasoning.
- Slice the duck breasts. Plate with the radicchio and garnish with the apples.