Preheat the oven to 200°C.
Fry the duck skin-side down in a medium-hot pan for 2–3 minutes.
Drain and discard the rendered fat from the pan.
Add star anise, orange zest, juice, and half the port to the duck.
Roast in the oven for 12–15 minutes until golden and slightly pink inside.
Transfer duck to a plate to rest.
Simmer remaining port in the duck pan, whisk in 50g butter, and season.
Sauté winter greens with remaining butter and water for 3–4 minutes.
Boil water, sugar, and spices for chutney, then add cranberries and port.
Simmer chutney for 3–4 minutes while mashing berries into a thick consistency.
Boil celeriac and potatoes in salted water for 12–15 minutes until tender.
Drain vegetables and blend in a processor with olive oil and butter.
Serve sliced duck over greens with mash and chutney on the side.