Interesting! I always wondered why.

I love, love, love popovers but I have the absolute worst time getting them out of the muffin pan. The pan I have is non-stick. I've tried to grease the pan with both butter and with oil. I end up getting mutilated popovers every time I make them, because they won't come out of the pan. Any suggestions?

I make popovers all the time and don't have any trouble getting them out. My method is to preheat the pan for 5-10 minutes until it's very hot, then pour ~1 tsp oil into each cup and then pour the batter in. I've also opened the oven door (although not in the first 10-15 minutes of baking) without any detriment.

I have finally mastered popovers after over a dozen failed (or semi-failed attempts). I read recipes and cook books and combined the most common suggestions to create the most perfect popovers that popped, were fluffy (not too eggy), and came out of the pan easily.

I opened the door in one recent batch to add another item to the oven and closed it quickly, but I did notice that they weren't as popped as the other batches.

My tips:
* Use room temperature ingredients (eggs, flour, milk, oil, cheese, etc.) Take it all out of the fridge a good hour beforehand. I've noticed if I forget to do this, it's not worth making. I have warmed things in bowls of warm water, however, they never come out perfectly that way.
* Make sure the pan has heated in the oven first (I put it in as the oven warms so by the time I'm done stirring everything and the oven is preheated, so is the pan)
* Use a special popover pan (muffin pans work, but never as well)
* Spray the cups down with baking Pam and then throw in a pinch of flour (this gets messy between the cups, so be prepared)
* Keep the oven door closes. I wish I knew the science of "why?" but all I know is that it does make a difference.
* Recipes that begin at a higher temperature and then are lowered seem to make the best finished product

The one thing I still haven't solved for is the post-oven deflation problem. I poke a hole in the top but it still goes down a bit. I just try to eat them as quickly as possible. Not too much of a problem there!

I had to go to Harold McGee's "On Food and Cooking", and dig for a bit to get what I think is the answer.

Part of it is heat, as you mention above; you don't want the heat to escape from the oven.

The second part is steam. To summarize what he says in his Baking section:

Steam escaping from the batter condenses on the surface of the dough, forming a film of water on the outside of the dough. This has two good effects: the first is to keep the surface of the dough from setting too quickly, allowing it to expand. The second is the condensed water transfers heat better into the dough, causing the gases trapped inside the dough to expand more quickly. Both of these contribute to "oven spring".

He says modern gas ovens do a poor job with oven spring. They have to vent their combustion gases, and the also vent the steam from the bread too quickly.

Opening the oven door allows the steam in the oven to escape, causing a lack of oven spring. Since a popover is almost entirely constructed from oven spring, this is a big problem.

As far as deflating post baking, I find that it mostly happens to underbaked popovers. If they have a nice golden crust, they stay puffed, no need to poke holes or do anything at all. Here's a really informative post on popovers from the King Arhur flour <a> blog.

Ack, bad link. Here it is.

I have tried the popovers a bunch of times and I have very little success getting them to pop. I wondered if the issue was my oven wasn't holding the heat high enough.

I'll try preheating the pan and give them another attempt tonight.

This is due to thermal expansion/contraction. A drop in temperature means less internal air/steam pressure in the puffs, which caused them to collapse. Once the puffs have a structure (the outside is crisp and rigid enough), it can handle the decompression. I bake them on high on the bottom rack and have no problems. The other thing that really matters for making puffs is how much egg to add.

So then what is this (nonsense?) I read about starting them in a cold oven. This suddenly makes even less sense to me than it used to.

I think it helps to start with a hot oven. The heat creates steam inside the dough making it puff like a balloon. But it can only grow if the dough is still stretchy, so it's good to heat the puffs quickly, before the outside turns into a hard shell. Likewise if you open the oven before the outside is done, the puffs can't handle the loss of steam pressure and deflate like a balloon.