Preheat the oven to gas 7, 220°C, fan 200°C. To make the soup, put the parsnips, carrot, onion, garlic and rosemary sprigs in a nonstick roasting pan. Pour the oil over and toss to coat. Spread out and season with pepper and the crushed chillies, (if using). Roast for 35-40 minutes, until tender and golden, turning halfway through.
Meanwhile, prepare the garnish. Draw a vegetable peeler down the length of the parsnip, and then the carrot, to make long ribbons. Pat dry on kitchen paper. Pour enough oil into a medium frying pan to cover the bottom by about 5mm (¼in). Heat the oil, then drop in the vegetable ribbons and fry for about 30 seconds, or until just starting to colour. Stir to stop them sticking together. Remove with a slotted spoon and drain on kitchen paper, then set aside.
Remove the rosemary from the roasting tin. Take out the garlic and squeeze it from the skins back into the tin. Stir in the stock, then ladle the soup into a food processor or blender, in batches if necessary, and purée until smooth. Pour the soup into a saucepan, pour in the cream and gently heat until warmed through. Season with salt and pepper to taste. Serve the soup in bowls, topped with the vegetable crisps.
Cook’s tip: To check when the oil is hot enough to fry the parsnip and carrot ribbons, drop a strip into the oil. If it sizzles straight away then it’s ready.
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