Heat oven to 200C/180C fan/gas 6. For the glaze, mix the honey with the spices and lots of cracked pepper, then set aside. Remove all the fat from inside the bird and, using the point of a small knife or skewer, prick the skin all over, paying particular attention to the areas under the wings and around the legs. Sit the goose in an empty sink and slowly pour over a kettleful of boiling water. Repeat the process a few more times (the more the better) until the skin is tight and glossy. Leave the goose to cool, then pat dry with kitchen paper.
Season the inside of the goose and stuff with the onions, halved garlic bulb, rosemary and orange. Rub the goose all over with the oil and season generously with salt. Sit the goose on a wire rack in a large roasting tin and tightly cover with a large piece of foil. Cook in the oven for 1 hr 30 mins.
Remove from the oven, discard the foil and use oven gloves to lift the rack (and the goose) out of the roasting tin. Pour all the fat from the tin into a bowl and set aside. Scatter the potato slices in the roasting tin, season with salt and mix with a small drizzle of the fat. Sit the goose back in the tin – on top of the potatoes – and cover with foil, then roast for 1 hr. Remove the foil, then brush the goose all over with the honey glaze and return to the oven for 15 mins. Transfer the goose to a large board or platter to rest, uncovered, in a warmish place for 30 mins.
Carefully pour away most of the fat from the potatoes. If your roasting tin is flameproof, finish browning the potatoes on top of the stove; if not, place the potatoes back in the oven until crisp and golden brown. Stir the parsley and the chopped garlic through the potatoes just before serving. Carve the goose at the table and serve with the potatoes.