Fry the bacon strips until beginning to crisp then add the sliced mushrooms and soften them.
Turn the chicken strips in the flour and thyme. Melt the butter in the bacon and mushroom mix and then add the chicken and all the flour that is left. Stir around until the chicken begins to colour.
Pour in the stock and Marsala, stirring to form a sauce and let this bubble away for about 5 minutes.
Pour into an ovenproof dish.
Roll out the pastry so that it is large enough to cover the dish and place over the chicken filling. Poke a couple of holes in the centre of the pastry to allow steam to escape.
Cook the pie for 20 minutes until the pastry is golden brown.