Heat your oven to 180°C/fan 160°C/Gas 4. Slash the skin on each duck breast a few times with a sharp knife. Sprinkle each breast with 1 tsp China 5 spice and some salt and pepper. Drizzle with ½ tsp olive oil each.
Rub the oil, spices and seasoning into the skin of each duck breast, making sure you rub it into the slashes. Pop to one side so they warm up to room temperature.
Pick any thick stalks out of the watercress so you just have tender shoots and leaves. Pop them in a bowl. Trim the spring onions. Finely slice the white part, then shred the green part into thin slices. Add them to the watercress.
Halve the cucumber. Take one half and slice in half lengthways. Scoop out the seeds with a teaspoon then finely slice the cucumber halves into thin crescents. Add to the salad. Toss together to mix. Pop to one side.
Warm a griddle or frying pan till it's smoking hot. Place the duck breasts in the pan, skin side down. Fry for 2 mins. Turn them over. Fry for 2 more mins.
While the duck cooks, measure out 1 tbsp of the tamari and 1 tbsp of the honey. Whisk them together. Pop the duck breasts onto a baking tray. Spoon the honey and tamari mix over the top.
Pop the duck in the oven for 8 mins (10 mins for well done). Take them out. Lift off the tray and wrap loosely in foil. Set aside for 10 mins – they’ll keep cooking as they rest.
Peel the skin off the duck breasts and discard (you can eat it, but that will increase the calories). Slice the duck breasts. Arrange the salad on the plates. Place the sliced duck breasts on top. Drizzle over any juices from the foil and serve straight away.