Preheat oven to 190°C/375°F/gas 5. Cut bacon into chunks and fry with thyme leaves. Add chopped leeks, fry for a few minutes then put a lid on, turn down heat and cook for 30 minutes, stirring occasionally.
Add turkey meat and mix in. Add flour, mix well then add stock. Add creme fraiche then bring to the boil
Sieve pie mixture, extracting the gravy for later. Put pie mix into a dish, cover with rolled puff pastry, slice and wash with the egg.
Bake in the oven for 35-40 mins, reheat the gravy and serve