Any time there’s a choux-based pastry on the blog, there are always a lot of calls for help with collapsing puffs. There are three fixes to the problem that I can think of. First, you can pipe higher. Which is to say, try to make your dough shapes a bit more vertical to begin with. You can achieve this in part by making sure you pipe your choux from a height of about half an inch above your surface. This way you “lay down” batter instead of spreading it.
Second, bake longer. Get a good brown on your puffs. This will make the walls of the pastry more rigid and less inclined to collapse. For larger shapes it’s a good idea to “vent” them by poking a hole in the bottom with a knife. This allows steam to escape and again helps the walls to dry out and remain rigid. Once you’ve done that you can return the puffs to the oven and turn the heat down to 250 degrees Fahrenheit for further drying. Keep the door propped open with the handle of a wooden spoon to prevent heat buildup and bake for a further half hour or so. If you like you can dry them out almost completely by turning the oven off at that point and letting the choux shapes sit as the oven cools, even overnight if you like.
Third, if after that you’re still having trouble you can increase the proportion of egg white. This is a time-tested Shirley Corriher trick (which reader Henry reminded me about this week) that helps give choux puff walls some rigidity. It works very well, though I find that if you make choux with craquelin you get all the rigidity without sacrificing moisture (egg whites tend to dry things out). However if craquelin isn’t in the plan, more white is a solid second choice.
Fourth, calibrate your oven. An oven that runs too hot can cause an overly aggressive rise at the outset of the bake. That creates a nice high rise, but as a consequence you get very thin walls that won’t support the weight of the puff once it starts to cool. Make sure you bake at 425 degrees Fahrenheit for only the first ten minutes, then lower the temperature to 375 for the remainder.