Choux pastry
A cooked paste raised entirely by steam, and the one pastry where the flour is gelatinised before it goes anywhere near the oven.
Also called pate a choux (INTERNATIONAL), choux paste (INTERNATIONAL), profiterole dough (INTERNATIONAL)
Choux is made by boiling water and fat, beating in flour to make a paste, cooking that paste briefly, then beating in egg.
Cooking the flour in boiling liquid gelatinises the starch before baking, which is what lets the paste hold a great deal of egg and still be piped. In the oven the water in the paste turns to steam, and because the gelatinised starch and egg protein form a skin that steam cannot escape through, the pastry inflates around a hollow centre. There is no chemical leavener and no yeast — the lift is steam alone.
The egg is added by feel rather than by count, because the quantity depends on how much water evaporated while the paste was being cooked. Correctly loosened choux falls from the spoon in a V and holds a piped shape without spreading.
A choux that has risen must dry out before it comes out. The structure is set but soft, and removing it early collapses it.
What it should be like
- Structure
- Hollow, with a thin crisp shell
- Volume
- Large expansion from steam alone
Why choux stays flat
Flat choux is nearly always too much egg or too cool an oven. Too much egg gives a paste too slack to hold a shape, so it spreads before the steam can lift it. Too cool an oven generates steam slowly, and the structure sets before enough pressure has built to inflate it.
Opening the door during the rise does both at once: it drops the temperature and releases the steam, and a partly-risen choux collapses immediately and does not recover.
Related
Part of
Pastry by convention and by use. Its method resembles no other member of the family.
What this product needs done
Structure building
UNUSUAL AND DELIBERATE: the starch is gelatinised on the hob before baking, which is what lets the paste hold so much egg and still be piped.
Gas retention
Egg protein and gelatinised starch form a skin steam cannot escape through. That skin is what makes the pastry inflate instead of merely drying.
Aeration
Steam alone. There is no yeast and no chemical leavener in choux, which is why oven temperature is not negotiable.
Hydration
The water is the leavening. Every bit of lift a choux gets is water in the paste turning to steam.
Techniques this product depends on
The egg is beaten into the cooked paste by feel rather than by count, because the quantity depends on how much water evaporated on the hob. No ingredient list can specify it.
Things that go wrong
The only product this fault applies to, because it is the only one raised by steam alone.
Pastry cream is lumpy, runny or grainy
The classic filling, and where a runny cream is most obvious.
Covered in
The pastry families, and what actually separates them
Covered by the guide, which is the resource a reader arrives at with this question.