Parsnip, spring onion and thyme gratin

Method

1. Heat the oven to 200°C/180°C fan/gas 6. Put the sourdough pieces on a large baking tray, then toss with 2 tbsp olive oil and the leaves from 4 thyme sprigs. Season with salt and pepper, then bake for 10 minutes until golden and crisp. Set aside. Turn down the oven to 180°C/160°C fan/gas 4.
2. Heat the remaining oil in a large pan or casserole over a medium heat, then cook the shallots and spring onions for 7-8 minutes until soft. Add the flour and stir for 3 minutes, then turn the heat to low-medium and add the double cream, milk, nutmeg and 2 thyme sprigs. Heat until just steaming. Add the parsnips and potatoes and cook for 10 minutes until softening. Season with salt and pepper, remove from the heat (discard any woody thyme sprigs), then stir in a third of the cheese.
3. Pour the vegetables and creamy liquid into the prepared baking dish, sprinkle half the remaining cheese on top, then bake for 30 minutes. Scatter the croutons on top of the gratin with the rest of the thyme and cheese, then bake for 15-20 minutes more until the top is golden brown and the gratin is bubbling. Serve with a sharply dressed green salad.