Preheat the oven to Gas Mark 6, 200ºC, fan 180ºC. Cut into quarters, or 5cm (2in) chunks if using large potatoes. Boil in salted water until just tender. Drain and then briefly return to the saucepan to dry out.
In a large roasting tin, pour in the olive oil. Add the potatoes, polenta and a good teaspoon of sea salt. Mix well, bashing them around the pan to crush the edges. Spread out into a single layer on a baking tray and roast for 30 minutes or until golden and crisp.
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