Pound salt, coriander, chilli, and cardamom in a mortar and pestle.
Stir in oil and rub the spice paste over the duck.
Fry duck skin-side down for 10 minutes until golden and crisp.
Drain excess fat and fry the other side for 4 minutes.
Rest the cooked duck in a warm place for five minutes.
Boil potato slices for five minutes then drain.
Fry potato slices in oil until golden and season well.
Simmer orange juice, zest, vinegar, turmeric, and sugar until syrupy.
Whisk olive oil into the warm orange reduction.
Plate potatoes, top with sliced duck, and drizzle with vinaigrette.