Preheat the oven to 200ºC, 180ºC, gas 6 and place a baking tray in the oven to warm. In a large non-stick frying pan, cook 3 duck breasts, skin side down, over a medium heat for 5 minutes until crisp, then turn over and cook for a further 2 minutes. Remove, cover with foil and set aside while you pan-fry the remaining duck breasts.
Transfer all 6 duck breasts to the warmed baking tray and cook in the oven for 15 minutes. Leave to rest for 5-10 minutes before slicing.Meanwhile, put the orange slices into the pan with the remaining duck fat. Cook for 2 minutes each side until golden, then set aside.Toss together the salad leaves, beetroot and orange slices.
Place salad on 6 serving plates. Slice the duck and arrange on the plate. Mix the dressing ingredients together and drizzle over the salad and duck to serve.