Add all the ingredients to a small saucepan and bring to a boil, then reduce and simmer for 20 minutes or until the mixture has reduced by a quarter.
Let cool completely and set aside. The mixture will thicken as it cools.
Pat the duck breast on both sides with a paper towel. Using a very sharp knife, make X-shaped incisions about 8 mm deep into the fat of the breast. Season the meat side with salt and pepper.
In a skillet, sear the duck breast over medium heat, fat side down first, until both sides are nicely caramelized* or about 5 minutes on each side.
Transfer the duck to a sheet of aluminum foil and let stand near the oven while you prepare the salad.
Divide the kale, cucumber, tomatoes, olives, pepper, feta, onion and fresh oregano between two plates.
Slice the duck breast about 1 cm thick and lay on top of the salad.
Drizzle with olive oil and a generous amount of the reserved balsamic reduction. Season with freshly ground pepper and fleur de sel, if desired.
*The breast is sufficiently caramelized when the fat easily comes off the pan. If there is any resistance, it is because it has not yet caramelized to perfection.
Recipe developed by Julie Zyromski
