Choux pastry contains neither baking powder nor yeast. Yet in the oven it triples or quadruples in volume and comes out entirely hollow. Steam alone is responsible.
How does the rise happen?
Choux pastry is high in water; roughly half its weight.
As the dough heats in the oven that water turns to vapour.
Water expands around sixteen hundred times on evaporating.
That expansion creates strong pressure inside the dough.
Because the dough is elastic it does not tear; it inflates.
At the same time the outer surface sets with the heat and forms a shell.
That shell holds the pressure in and the dough expands upward.
Once the steam escapes, an empty shell remains.
The cavity inside a profiterole is the space the steam left behind.
Why is the starch cooked first?
That is the most distinctive step in choux.
The water, milk, butter and salt go into a pan and come to the boil.
The flour goes in all at once and is cooked on the hob with stirring.
The starch gelatinises at that stage.
Gelatinised starch binds water and makes the dough elastic.
That elasticity is what allows it to withstand the steam pressure.
Without gelatinisation the dough tears under pressure and does not rise.
Cooking takes two or three minutes; it is complete when the dough pulls away from the sides of the pan and forms a ball.
A thin white film forming on the base of the pan is another indicator.
Overcooking separates the fat; the dough looks glossy and greasy.
| Stage | Temperature | What happens |
|---|---|---|
| Boiling | 100 °C | Fat melts, water boils |
| Cooking the flour | 80-90 °C | Starch gelatinises |
| Cooling | Below 60 °C | Preparation for egg |
| Adding egg | 50-60 °C | Consistency is set |
| First bake | 200-220 °C | Steam raises it |
| Drying | 170-180 °C | The shell hardens |
How is the egg ratio set?
Egg is the only variable component in choux.
It provides both liquid and protein.
The liquid brings the water that produces the steam.
The protein coagulates during baking and fixes the structure.
The quantity is not fixed; it depends on how much water the dough lost.
The water evaporating during the flour-cooking stage differs every time.
Egg is therefore added little by little with the consistency checked.
A general ratio: four or five eggs for 250 millilitres of liquid, 150 grams of flour and 100 grams of butter.
But the last egg always goes in partially.
Too much egg makes the dough fluid; the product spreads and does not rise.
Too little makes it stiff; the rise falls short and the product cracks.
How is the consistency tested?
Two tests are used.
The first is the spatula test. Lifted on a spatula, the dough should fall slowly and form a V at the tip.
That V should hang for three or four seconds without breaking.
If it breaks immediately the dough is stiff; if it runs quickly it is too soft.
The second is the line test. A line is drawn across the surface with a finger.
If the line closes slowly the consistency is right.
If it closes immediately the dough is too fluid; if it does not close at all it is too stiff.
The dough should be tested while warm; cooled dough gives a misleading result.
The dough temperature should not exceed 50 to 60 degrees while adding egg; in hot dough the egg cooks.
What should the oven curve be?
Choux bakes in two stages.
The first is high heat: 200 to 220 degrees.
That stage runs fifteen to twenty minutes.
The high heat turns water rapidly to steam and the rise happens here.
The outer shell sets at the same time.
The second stage is lower heat: 170 to 180 degrees.
That stage runs another fifteen to twenty minutes.
Its purpose is driving moisture from the interior and hardening the shell.
Skip that stage and the product collapses once out of the oven.
With the shell insufficiently dried it cannot carry its own weight.
The total time is thirty to forty minutes.
Why must the door stay shut while choux bakes?
This is the commonest mistake.
The door must never be opened in the first twenty minutes.
Opening it drops the temperature inside and lets steam escape.
The internal pressure falls abruptly.
If the shell has not yet set the dough collapses and never rises again.
That collapse is irreversible.
In the second stage, once the shell has set, the door can be opened briefly.
Some recipes even leave it ajar for the last five minutes, which speeds the escape of moisture.
Checking should be done through the oven glass; the second stage begins once the product has clearly risen and turned golden.
How is it hollowed and filled?
A baked profiterole can retain some damp dough inside.
That wets the product and shortens its life.
A small hole is made in the side of each one immediately after it leaves the oven.
That hole lets the steam out.
The product cools on a wire rack; cooled on a tray it draws moisture from underneath.
Once completely cold the damp pieces inside are cleared out with the tip of a fork.
Filling goes in through the same hole with a piping bag.
Once filled the product should be eaten quickly; cream softens the shell within a few hours.
In a business, filling should happen close to service.
What changes when choux is frozen?
Choux can be stored in three forms.
The first is as raw dough. Piped shapes are frozen on a tray and then bagged.
They go into the oven without thawing; the time lengthens by five minutes.
That is the most practical method and the result comes very close to fresh dough.
The second is baked and empty. The baked shells are frozen.
They keep three months.
Before use they are heated at 160 degrees for five minutes, which restores the crispness.
The third is filled. That is the least preferred; the shell takes up moisture during thawing and softens.
In cream-filled products the texture deteriorates after thawing.
The first two methods are practical for businesses; the dough is made once and used over weeks.
