Bring a large pan of salted water to the boil and cook the potatoes for 6-8 mins until the outsides are starting to soften. Drain well, then leave to steam-dry for a few minutes. Will keep covered and chilled for up to two days. Return the potatoes to the pan, add the flour, put the lid on and shake well to coat the potatoes and fluff them up.

Meanwhile, heat the oven to 200C/180C fan/gas 6. Pour the oil into a deep roasting tin and put in the oven to heat for 5 mins. Take out of the oven and carefully spoon the potatoes into the hot oil, then baste in the oil so they’re well coated. Spread them out to a single layer and put in the oven to roast for 20 mins. Turn and baste again, roast for another 20 mins, then repeat and roast for a final 15-20 mins or until golden and crisp. Scatter over all but a couple of tablespoonfuls of the parmesan, then put back in the oven for 2 mins so the cheese melts.

Remove the potatoes from the tin, leaving as much oil behind as possible, and pile onto a platter or on a serving dish. Scatter over the remaining parmesan, give the platter or bowl a shake, then drizzle over a little truffle oil (we used 1/2 tsp, but use as much as you like).