March 21, 2010

Collapsing cream puffs

I made a batch of eclairs today, and I finally realized why cream puffs and eclairs that come out of the oven looking perfect end up a flattened, squished-up mess. Figured I'd write it down so I wouldn't forget, and maybe it'll be useful for other folks in the same circumstances.

When I make cream puffs I use the recipe from Rose Beranbaum's The Pie and Pastry Bible. Page 530, for the curious. It's a handy book and a really nice recipe -- it uses whole eggs and a food processor for the final mix-in of the eggs, which is great. I can make a batch without killing my forearms and they come out really well.

The only problem I ever have is that the puffs, once they're out of the oven, seem to end up flat. Not all of 'em mind, they start out fine but by the time I get to the end of a set (I normally get three dozen puffs out of a recipe) the pastry's pretty much useless. Flat and unpleasant, and even once they're finished drying the insides are a bit gummy. You can forget about filling them too, as there's no room inside for filling and they don't expand.

Well, I finally figured out why and, more importantly, I figured out what to do about it.

The problem here is air pressure. (Which, as I used to watch Beakman's World all the time, you'd think I'd have realized, but alas not) Puffs puff because the water inside turns to steam and pushes the pastry apart. You get great big bubbles inside ready for pastry cream or whipped ganache or mousse or whatever -- the dough inflates like a balloon with the steam.

You have to take the pastry out of the oven to poke a hole in them to let the steam out, otherwise the inside gets all gummy. That balloon inside, though, is still sealed, which is where the collapse comes in. If the insides cool down the gas inside the pastry shrinks (PV=nRT and all that) and the resulting semi-vacuum makes the puffs collapse. The insides are still damp from the condensing steam so that collapsed cavity basically glues itself together and becomes un-inflatable.

The reason the initial puffs are fine is that you put a hole in them before the gasses inside cool, shrink, and possibly condense. That hole lets the cooler outside air in, allows the pressure to equalize, and that means no collapsing puffs and things are much, much better. (And tastier)

Every cookbook I have says the point of the hole is to let the steam out and keep the insides from getting gummy, but I dunno if that's actually true. The 'not collapsing because of pressure changes' seems more likely. Anyway, it doesn't matter which explanation's the right one here, just that the hole is your friend.

The secret, then, to a full batch of non-collapsing puffs is to put the hole in fast, and to keep the puffs you aren't working on yet as hot as you can. If a batch makes only a single sheet pan of puffs (like eclairs do) then make two sheets and keep the one you aren't working on still in the oven. If you've made two full pans (because you made cream puffs) then make the holes as fast as you can, preferably with the pans still in the oven. Pull the rack out and jab really fast with your knife or thermometer (instant-read thermometers make good cream puff holers) and you'll have yourself a set of nice, un-collapsed cream puffs.

Posted by Dan at March 21, 2010 11:00 PM | TrackBack (0)