2kg large potatoes, thinly sliced (a mandolin is ideal)
300g white onions, finely sliced
500ml fresh chicken stock
Heat oven to 200C/180C fan/gas 6 and grease a large casserole dish. Melt the butter in a large frying pan over a medium heat. Toss in the bacon and season really well. Cook until golden and crisp, about 5 mins.
In a large bowl, gently mix the potatoes with the onions, bacon and some more seasoning. Spoon the mixture into the prepared dish and pat it all down, pouring over the stock.
Bake in the centre of the oven for 1 hr 45 mins, covering the potatoes after an hour to stop them getting too dark. You should be able to push a knife through the potatoes with little resistance when the dish is cooked.