Preheat the oven to 200°C.
Season the goose breast with salt and pepper and sear in a hot oven-proof frying pan skin-side down for 5 minutes.
Turn the goose and cook for another minute before draining the fat.
Transfer the pan to the oven and roast for 10 minutes until cooked through.
Remove goose from the pan and set aside to rest.
Parboil the swede chunks in boiling water for 8 minutes and drain.
Melt butter and oil in an oven-proof pan, add chestnuts and swede, and roast in the oven for 5 minutes.
Melt butter and oil in a saucepan and sauté leeks for 5 minutes until soft.
Add cranberries, vinegar, and sugar to the leeks and cook for 5 more minutes.
Serve the roasted goose with the swede and chestnuts, topped with the leek and cranberry sauce.