I often use bought puff pastry to make a topping for a chicken pie. However, I tend to find that the pastry is fully cooked on the top but the underside of the pastry remains almost raw. How can I avoid this?
A few points to consider...
1) Try docking the pastry. Docked portions of pastry will rise more than undocked portions. This will promote even cooking.
2) In general, to cook food more evenly, one should cook longer at a lower temperature. The problem is that the dough on the bottom of your crust is not reaching a high enough temperature by the time the top of your crust is done cooking.
3) Puff Pastry is notoriously finicky. Be sure to handle the dough according to puff pastry best practices to ensure the layers do not collapse and stick together.
Pepperidge Farm has a tutorial website (http://www.puffpastry.com/videos-and-tips#howto-demos) to help people with puff pastry issues, but it doesn't appear to cover much detail.
I am going to try baking the pie crust on it's own on a baking tray. It's what most restaurants seem to do. Wish me luck.
So long as the filling is moist (and that's most of the point of a pot pie), the filling is going to steam the underside of the pastry, resulting in the dough cooking more slowly.
Starting with a hot filling will help, as will cutting vents to allow the steam to escape, but you also need to try to ensure that the pastry doesn't actually touch the filling. (as you then also have to deal with the filling being a thermal sink).
Smaller ramekins, not filled to the top, with the pastry stretched over the rim should sag less, and hopefully set up some before it sags down to touch the filling.
Or you can cheat, and cut disks that are a little smaller than the size of the vessel the pot pie is to be served in, bake them on a sheet tray, and then drop them on top just before serving. (You might also be able to bake them part way, and then drop them in to finish baking, so it's not quite so obvious what you did)
I assume you are add pastry to the top of an oven proof dish filled with your chicken pie!
Have your rolled pastry ready in the fridge.
If you have a read of this it'll give you an idea of how puff pastry is made! I wrote it a long time ago but nothing's changed since then!! ;)