Make sure the butter and water are cold before you start to make the pastry.
Finely dice the butter, add it to the flour and rub with your fingertips until the mixture resembles fine breadcrumbs. Make a well in the centre of the bowl and add most of the water and a pinch of salt.
Mix the dough without overworking it: you just want to bring the ingredients together.
Roll the mixture into a ball, flatten slightly and cover with cling film. Allow to rest in the fridge for at least 30 minutes. When you are ready to top the pie, roll the pastry out to a thickness of 5mm. Brush the edges of the pie dish with egg wash and place the pastry on top. Trim the edges and score a pattern in the top if desired.
Preheat the oven to 180'C.
Cut the thighs into 1 inch dice, dust in the flour and season with the salt and pepper. Cut the leek into small dice. Peel and finely dice the garlic.
Heat a large saucepan over a medium heat and add the butter. When melted, add the chicken and brown on all sides. Add the carrot and cook for 2 minutes before adding the leek. Cook for a further minute, add the garlic, thyme, chicken stock and cream. Cook for 20 minutes over a medium heat, stirring while the mixture reduces and thickens.
Once cooked, allow too cool a little then top with the pastry. Brush the remaining egg on to the pastry and bake for around 25 minutes or until golden on the top.
«Try adding diced pancetta and Dijon mustard for more depth of flavour in this dish.»