I have been successfully making choux a few times as of late. Then it struck me one day when my my batter just flopped in the oven. Well, they weren't really flopped, or deflated or anything. They just didn't rise at all.
The 10-cm fully-baked choux came out pretty much the same size as when they went into the oven, no puff, no air pocket for the filling or anything. Imagine bread sticks that waiters bring to your table when you visit Italian restaurant, that what they looked like. Despite disappointing result, they tasted great, tasty and buttery, a bit better than salty crackers. I was thinking whether they could perhaps become one of the most popular finger snacks ever made. Um, I got drifted away. However, the whole tray went directly to the trash.
There are a few things I want to share, not sure though if my theories are correct. I have been trying to google the instructions, to see if anyone talked about things that have been clogging my mind, none mentioned in details how the batter should be cooked in the pot , which I think IS the key to success. None even mentioned how batter consistency should be like before baking.
Here are un-confirmed theories of mine based on lecture in class and 7-8 repetitions at school and home.
- Choux batter needs to absorb as much as liquid as possible since it needs moist/steam to push up its structure in the oven (there are no other structure-builders such as yeast or baking powder here). This is achieved through gelatinization process where starch swells hot liquid while cooked in the pot, the target temperature of the batter is around 60-65 C.
- The swelling process begins when you dump all the flour, all at once, into boiling water (this is done off heat) Why "all at once"? I presume adding flour little by little would quickly over-cook the flour into dumplings. Also, the all-at-once thingy brings down water's boiling point to target gelatinized temperature around 65-70 C degree.
- The purpose of precooking/drying dough in the pot until it dries out/or so called "forms a ball and leave thin film at the bottom" is to
1) complete the gelatinazation process , to let the mass of clumped starch evenly heated. Also keep in mind that you need the dough to be as hot while stirring (optimum temp is 60-70 c, which is why most instructions advice medium heat***) . 2) to dry out the dough as much as possible so it can absorb liquid from eggs at its best capacity in later steps.
*** I have seen my classmate did the precooking at very high heat (we had exam, and she was in a hurry) I presumed she must have stirred it crazily quick, or the dough could have burnt. For me I used the medium heat and stir at my snails pace until the dough's consistency was similar to that of almond paste (or clay).
- Cool down the dough before adding eggs, little by little, otherwise they coagulate. Of course , you want choux batter, not omelet.
And here comes last part (but not least) before piping, it's when we add eggs. Yes, sounds simple but read this carefully, I believe this tip is the secret in making 1) well-puffed 2) well-shaped choux.
- When you add eggs half way through, notice whether the batter becomes too runny to pipe (see batter texture we want to achieve below). If it is, bad news, the dough is not sufficiently cooked/dried out in the pot, thus low-absorption ability. If this happens in class, chef would advice throwing this away and start over. If this happens at home, you may continue to add more eggs as called for and bake. It still puffs up nicely but keep in mind the batter is too runny, it won't hold any shapes as you wish it would. Alternately, you can fry Churros/Funnel cake using this batter.
- The goal we want to achieve - batter must be pipable, not too stiff/too dry to pipe that it rips off the piping bag, not too soft that it cannot hold the shape or flats out right away when piped on baking sheet. Below is a sample of the batter. To test, with the spatula, scoop up the batter, if it drops down and leave hanging V-shape , it's good to go. Or, when you drag finger to cut through the dough, it slowly pulls back on , covering the gaps.
Now, I found a lot of websites left out these critical parts of how the dough consistency should be like. Of course baking choux is easy, but making it nice and pretty is not as easy as it seems. Most amateur bakers don't cook the batter properly in the pot. And they continue adding eggs as the recipe calls for, no matter how runny the batter is and end up having flat choux (although they have satisfying big air pockets). Some instructions advice us to stop adding eggs whenever we achieve piping consistency/texture, regardless of (too) little eggs we've added. Result? too little eggs, not enough liquid, not enough steam in the oven thus no push-up for the choux. Final products are weird looking buttery bread sticks with no air pockets just like what I experienced.
- Oven temperature - If you have fan forced oven, 170-180c would be appropriate. For bakers oven , it's 190-200 c for the first half and 180 c for the rest. Baking time depends largely on the shape of the choux and how crowded you lay them on the tray. So you may check for the doneness 1) surface is evenly golden brown, no white streaks appear on the cracks 2) it springs back when gently push and 3) the bottom is evenly brown out. Be careful not to open the oven door too early, before they fully rise otherwise the steam will escape and they will collapse. Nothing can be done to fix that.
Do not crowd the tray, for some reason, it would take a lot longer to bake them through. And then, if you happen to open the oven before they puff, you know you would regret.
I won't mention the process after baking such as poking /cooling down and filling. There are some other tips which I haven't tried such as spraying water into the oven before baking to increase steam. I personally do not think it would help largely because the steam that help pushes the choux is trapped inside starch molecules. Well, if anyone can back this spraying tip with your experiment, please do let me know.
And here is a very informative website I found, with lots of beautiful illustrations. He mentioned a good trick to prevent cracks on surface. I haven't tried the mix of bread+pastry flour, which is interesting. If anyone tried, again, please let me know the result.
Hope your choux shines !