Chicken and mushroom pie

Method

1. Preheat the oven to 200°C/fan180°C/gas 6. Put the chicken, bay leaves, onion and stock in a pan. Bring the stock to a simmer and poach the chicken for 10 minutes, until cooked through. Remove the chicken and chop into pieces. Reserve the stock.
2. Meanwhile, put the leeks and 200ml water in a deep, non-stick frying pan and cook for 5 minutes, until the water has evaporated. Add the oil, thyme and mushrooms and fry for 2-3 minutes, stirring. Stir in the flour, then gradually add the chicken stock and bubble for 7-8 minutes, until thickened. Remove from the heat and stir in the chicken, yogurt and mustard (if using). Season. Remove the bay leaves and pour into a 24cm x 20cm ovenproof dish.
3. Brush both sides of the filo pastry sheets with egg and layer on top of the filling, scrunching the top layer. Bake for 20-25 minutes, until the filling is bubbling (cover with foil if the pastry is browning too much). Serve with seasonal vegetables.