Boil the parsnips for 5 mins, then drain well and let them steam-dry for a few mins. Mix the mustard powder with the flour and plenty of seasoning. Toss the parsnips in the mix, then shake off any excess.
Heat oven to 220C/200C fan/gas 7 – you can do this while the turkey is resting. Put the oil into one large, or even better 2, non-stick baking trays (the parsnips mustn’t be crowded if they’re to become really crisp), then heat in the oven for 5 mins.
Carefully scoop the parsnips into the fat, turn them a few times, then roast for 30 mins or until golden and crisp.
Drizzle the honey over the hot parsnips, give them a little shake, then scatter with flaky sea salt and tip into a serving dish.