Pre heat your oven to 180C. To a large frying pan on a medium to high heat add olive oil followed by your onion. Fry for a few minutes and then add your leeks, garlic and carrot and fry for another 5 minutes, until everything starts to soften.
Add your cooked chicken, mixed herbs, salt, black pepper and gluten free flour., stir so everything is coated. Turn the heat down to low and then add your chicken stock and bay leaves and simmer for a few minutes. Add the cream and simmer for another few minutes, it should start to thicken up slightly. Remove the bay leaves.
Transfer the filling to a pie dish and then top with a gluten free puff pastry sheet. Brush with egg and bake in the oven for around 35 minutes, until golden brown.