Leek and sweet potato gratin
Preheat the oven to 180C/350F/Gas 4.
Heat the oil and butter in an ovenproof frying pan over a medium heat. Fry the onion and leek for 3-4 minutes, or until softened. Add the sweet potato and fry for a further two minutes.
Add the wine and simmer for 1-2 minutes until the liquid has reduced. Add the cream, season to taste with salt and freshly ground black pepper, and stir well.
Transfer the pan to the oven and cook for 10-12 minutes, or until the potatoes are cooked through and the cream is bubbling.
To serve, spoon onto a serving plate and serve immediately as a side dish.