Can be part-cooked for about 45 minutes up to 24 hours ahead.
To serve, return to the oven without the foil for about 20-30 minutes, or until piping hot.
Freezes well cooked.
750g sweet potatoes, peeled
750g King Edward potatoes, peeled
300ml double cream
150ml chicken or vegetable stock
50g Parmesan cheese, grated
Preheat the oven to 220°C/Fan 200°C/Gas 7
You will need a 2-2.4 litre shallow ovenproof dish, buttered.
Slice the sweet potatoes and King Edwards very thinly using a sharp knife or the slicing blade on a processor.
Arrange one layer of mixed potatoes in the buttered dish.
Season with salt and pepper and drizzle over a little cream and stock.
Continue to layer the potatoes and double cream and stock until you have used all the ingredients.
Push the potatoes down into the liquid using your hands so they are all covered.
Sprinkle with the cheese and cover with foil.
Bake in the preheated oven for about 40 minutes.
Remove the foil and continue to cook for another 25-30 minutes, or until golden brown and the potatoes are cooked through.
Leave to stand for 5 minutes before serving.
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