Pre-heat oven to 400°F/200°C/Gas 6
Put some olive oil and butter into a large saucepan over medium heat.
Add the leeks and cook for a few minutes before seasoning with salt, pepper, and herbs.
Turn the heat down and simmer for 20 minutes, stirring every now and then.
Add the fresh cranberries and cook for a further 10 minutes.
Add the leftover turkey, bacon-wrapped sausages, chestnuts, and dried cranberries, and stir everything to combine.
Add the flour and mix well to coat everything, then add the chicken stock.
Bring the stock to a boil, and check your seasoning, adding more if desired.
Strain the mixture through a sieve and catch the sauce in another pan. Reserve this to use as the gravy when serving.
Line a 9x13" casserole dish with four or five sheets of filo pastry, brushing with a little oil between each layer.
Transfer the pie filling to the dish and then cover with the rest of the pastry, again brushing with a little oil between each layer.
Brush the top layer of pastry with oil and bake in the oven for 25-30 minutes until the pastry is golden.
Serve with the reserved gravy (which will need heating up) and enjoy!