Preheat the oven 180°C, 160°C Fan, Gas Mark
Melt the butter in a large non-stick ovenproof frying pan (about 24cm), add the mushrooms and cook for 3-4 mins.
Stir in the flour, cook for 1 min, then gradually pour in the stock, stirring continuously, until the sauce thickens.
Reduce the heat and simmer for 2-3 mins.
Stir in the pork, spinach, parsley and crème fraîche. Season. Remove from the heat.
Scrunch up the sheets of filo pastry, then arrange over the top of the pork mixture to completely cover. Spray the pastry with the oil, then cook in the oven for 20 mins until the pastry is golden and the pork is cooked through.
Serve with seasonal vegetables.