Extra-crunchy parmesan roasties

Method

1. Heat the oven to 200°C/180°C fan/gas 6. Put the potatoes in a pan of cold salted water and bring to the boil. Simmer for 10-15 minutes until tender when pierced with a round-ended knife. Drain, reserving 600ml of the cooking water for the turkey gravy, then put the potatoes back in the pan, off the heat, to steam dry. Roughen the edges a little by shaking the pan (this will give extra crunch when the potatoes are roasted).
2. Heat the oil in a large roasting tin in the oven until smoking. Add the potatoes and toss to coat. Roast for 30 minutes, then add the cornmeal or polenta and toss to coat. Return to the oven for 10-15 minutes until crunchy. Serve scattered with the parmesan and thyme leaves.