Turkey & sweet leek pie

INGREDIENTS

• 2 rashers higher-welfare smoked streaky bacon, roughly chopped
• ½ bunch fresh thyme, leaves picked
• olive oil
• 2 kg leeks, washed, trimmed; white end chopped into chunks, green end finely sliced
• sea salt
• freshly ground black pepper
• 800 g cooked white turkey meat, torn into big chunks
• 2 heaped tablespoons plain flour, plus extra for dusting
• 2 pints organic turkey, chicken or vegetable stock
• 2 tablespoons crème fraîche
• 500 g puff pastry
• 12 jarred or vac-packed chesntnuts, roasted and peeled
• 2 sprigs of fresh sage, leaves picked
• 1 free-range egg, beaten