For the dressing, melt the butter in a saucepan and gently cook the onion until soft. Add the orange juice and boil until almost dry then add the cherries and flambé with the kirsch, if using. Add the wine and jam and cook until you have a syrup then season with sea salt and freshly ground black pepper and remove the pan from the heat.
For the duck, score closely spaced parallel lines into the skin of the breasts with a very sharp knife. Season with sea salt and freshly ground black pepper then place skin side down in a dry frying pan over a medium heat. Cook for 10 minutes without turning until the fat has been released and the skin is golden-brown and crisp. Turn the duck breasts over and continue cooking for a few minutes until the meat is cooked medium-rare to medium. Remove the duck from the pan and set aside to rest in a warm place. Reserve the fat in the pan.
Meanwhile, boil the turnips in salted water until just tender then drain well. Mix in the butter and season with sea salt and freshly ground black pepper. Add the spinach and allow it to wilt. Fry the chanterelles in a little of the duck fat for a couple of minutes then season with sea salt and freshly ground black pepper.
For the orange and herb butter, place the orange juice in a small pan and boil until reduced by two thirds. Whisk in the butter, season with sea salt and freshly ground black pepper then stir in the chopped herbs and remove the pan from the heat.
To serve, carve the duck breasts into slices and arrange on warmed plates. Add the vegetables then spoon over the dressing and finish with the orange and herb butter.