Preheat the oven to 220°C (fan 200°C/gas seven)
Slice the sweet potatoes and King Edwards very thinly
Arrange one layer of mixed potatoes in the buttered dish. Season with salt and pepper, and drizzle over cream and stock
Continue to layer the potatoes, 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 cheese and cover with foil
Bake in the preheated oven for 40 minutes
Remove the foil and continue to cook for another 25 to 30 minutes
Leave the dish to stand for five minutes before serving