Heat the oil and butter in a large, shallow ovenproof casserole dish. Add the onion and cook for 10 mins until really soft. Push the onion to one side of the dish and add the sausages, browning them all over (skip this step if you’re using cooked leftovers).

Remove the sausages from the dish and set aside to cool a little. Stir the mustard powder, flour and stock cube into the oil and butter for 1-2 mins, then add the white wine. Bubble for 1 min, scraping the bottom of the dish to release any tasty bits, then add the stock. Stir to make a smooth sauce, season and bubble for 5 mins. Heat oven to 200C/180C fan/gas 6.

Cut the sausages and stuffing into bite-sized chunks, add to the sauce with the turkey, mustard, crème fraîche and parsley. When bubbling, remove from the heat. Crumble the potatoes in your hands over the top of the filling, so you have some larger and smaller chunks. Scatter with cheese and bake for 40 mins until the potatoes are crisp and the filling is bubbling around the edges.