Preheat the oven to 200°C (400°F / Gas 6) and slide a baking tray inside to heat up.
Score the duck skin in a diamond pattern with a sharp knife, cutting the fat but not the meat. Season well with salt and pepper.
Lay the breasts skin-side down in a cold ovenproof frying pan, then set it over medium-high heat. Cook for about 7 minutes, until the fat has rendered and the skin is crisp and golden.
Turn the breasts over and move the pan to the oven for 3 to 4 minutes. Lift the duck onto a warm plate and rest for 2 to 3 minutes.
Return the pan to the hob, add the pak choi and cook for 2 minutes until it takes some colour. Pour in the orange juice, soy, ginger and butter, bring to a simmer, then stir in the honey and reduce to a thick sauce.
Slice the duck at an angle, plate with the pak choi and rice, spoon the sauce over and scatter with sesame seeds.
