Whisk all dressing ingredients together in a small jug until emulsified. Taste and adjust seasoning to your own liking.
Mix the slaw ingredients together gently in a bowl. Set aside.
For the duck, remove it from the fridge at least 15 minutes before cooking - this helps regulate the temperature when cooking. Score the fatty skin with a criss-cross pattern and sprinkle with salt.
Heat the element to medium-high but keep the pan cold (this helps the fat come off the breast). Place the duck skin-side down in the pan and put on the heat.
Preheat the oven to 190C.
Allow the heat to increase and spoon off the fat as it pools in the pan (you can use this for your roast potatoes if you're cooking them). Once it's golden brown, flip the breast over to sear it for about a minute, then place in a roasting tray skin side up.
Place in the oven and cook for about 10 minutes, and then remove the roasting tray and rest for 5-10 minutes. Slice each breast and serve on the plate with a pile of slaw, and then drizzle the dressing over the slaw and the duck.