Whisk together 250ml of white wine, 2 tablespoons of plain flour and salt + pepper. Either whisk it in a jug, to measure the wine, or directly in your slow cooker pot to save effort.
Add your chicken and the mushrooms.
Crumble in a stock cube or add a stock pot.
Add a little thyme, tarragon or rosemary depending on your preferred flavour.
Cook on low for 8+ hours. If you want to keep larger chunks of chicken then used diced chicken and cook for 4-5 hours on low or 3 hours on high.
Pour your filling into a pie tin.
Melt your butter.
Dip your filo pastry sheets in and then lay on top of the slow cooker chicken mushroom pie filling.
Cook at gas mark 5 (190C) for 25-30 minutes. As soon as the top is golden brown it is ready for serving.