Rinse the duck under cold water and pat dry with kitchen paper.
Season with salt and pepper, fill the cavity with herbs and 125ml water, then seal.
Chill in the fridge for three hours and return to room temperature before cooking.
Preheat the oven to 220°C.
Place the duck on a wire rack over a tray, pour 375ml boiling water over it, and sprinkle with vinegar.
Add onion halves to the tray, lay bacon over the breast, season, and cover tightly with foil.
Roast for 30 minutes, then remove foil and bacon, reserving the bacon and onions.
Reduce the oven temperature to 180°C.
Simmer milk with onion, cloves, peppercorns, mace, and salt in a saucepan.
Infuse the covered milk mixture off the heat for one hour.
Return the duck to the oven for one hour, basting every 30 minutes.
Rest the duck for 40 minutes and separate the meat juices from the fat.
Strain the infused milk over the breadcrumbs and soak for five minutes.
Heat the bread sauce until thickened and stir in the butter.
Sauté the reserved onions in the roasting tray juices for 3 minutes.
Combine the internal duck liquid with the tray juices and reheat for gravy.
Return the duck and bacon to the oven for 15 minutes to crisp the skin.
Carve the duck and serve with onions, crumbled bacon, gravy, potatoes, and vegetables.