Not quite a chicken pot pie as we are not making a pie crust nor are we using pastry on the bottom of the filling. But this way is very easy and really tasty. Using puff pastry gives this dish a buttery richness without a soggy bottom. You can always use ready-cooked chicken but buying raw chicken breasts is usually more economical and (in my opinion) tastes better. You can make these in advance and freeze them before baking.