Pastry cream
A starch-set custard with a delayed failure mode: an enzyme in the yolks digests the starch overnight unless the cream was genuinely boiled.
What makes it set
Gelatinised starch, and Protein setting
A baked product is set by the oven. This one is not — and what sets it instead decides almost everything that can go wrong with it. See the whole family by mechanism.
Also called crème pâtissière (INTERNATIONAL), creme patissiere (INTERNATIONAL), confectioner's custard (UK), custard (UK) — Used loosely. A pouring custard is set by egg alone and behaves differently — see below.
Pastry cream is milk thickened with egg yolk and a starch — cornflour, or flour, or both — and cooked until it sets. It is the filling in a fruit tart, a choux bun, a mille-feuille and a Danish, and it is the base of several other things: lightened with cream it becomes a diplomat cream, beaten into butter it becomes a German buttercream, folded with meringue it becomes a chiboust.
Two mechanisms set it and it matters which is doing more. The starch gelatinises, swelling and thickening the milk; the yolk protein coagulates, adding richness and some set of its own. Because the starch is there, pastry cream can be boiled — the starch protects the protein from setting into lumps — and unlike a pouring custard it must be.
That requirement is the most consequential thing on this page, and it is the one most often left out.
What holds it together
A gelatinised starch gel holding milk, with coagulated egg yolk protein dispersed through it and contributing both set and emulsifying capacity for the yolk's own fat.
Follows from BakeHQ's starch gelatinisation and protein coagulation records, which carry the citations for both mechanisms.
RecordedFollows from evidence recorded elsewhere on BakeHQ
What temperature does to it
It must reach a full boil and be held there briefly, which is not the same as reaching the point where it thickens — the starch gelatinises and the mixture looks finished well before the temperature is high enough to destroy the yolk's starch-digesting enzyme. Taken off early it sets, chills, and is liquid again by morning. Cooked too hard or too long after that point it goes rubbery and can weep fat.
Supported by a professional body rather than by a measurement. It carries the direction — boil it, or the starch is digested — and nothing quantitative, so no rate and no temperature is stated here.
RecordedAmerican Society of Baking
How it keeps
Chilled fast, covered directly on the surface, and used within a couple of days. It is a low-acid, high-moisture preparation containing cooked egg and milk, and it is one of the few things in this catalogue where the storage advice is about safety as much as quality. It does not freeze: the starch gel separates on thawing and weeps.
Standard patisserie practice. BakeHQ makes no food-safety judgement and the relevant national authority is the right source for one.
RecordedEstablished practice, not a measured result
What a good one is like
- Texture
- Smooth and glossy, with no lumps and no perceptible starch grain
- Structure
- Holds its shape when spooned but softens under the spoon; not rubbery or sliceable
- Flavour
- Tastes of milk, vanilla and egg — never of raw starch
Where it stops
Pastry cream cannot be used as a structural layer: it holds its own shape and nothing else's, so a tall cake filled with it will slump unless it is stabilised with gelatine or lightened with something that is. It will not freeze. It weeps if it sits on pastry for long, which is why a tart is filled late and often sealed with chocolate first. And the starch that makes it robust also makes it opaque and slightly heavy — a set custard tart or a crème anglaise, both set by egg alone, taste noticeably cleaner and neither can be boiled.
Tasting of cornflour and never setting are the same fault
Two of the commonest complaints about pastry cream turn out to be one thing seen from different angles.
Raw starch has a distinct chalky flavour, and it disappears when the starch is fully cooked out. A cream taken off the heat as soon as it thickened has gelatinised starch — which is what thickened it — but has not been held at the boil, and both the flavour and the enzyme survive that.
So a cream that tastes faintly of cornflour is telling you, at the moment you make it, that it is also going to be thin tomorrow. It is the earliest available warning of the delayed failure, and it is available while there is still time to put the pan back on the heat.
Where a pouring custard differs, and why it cannot be treated the same
A crème anglaise is milk, sugar and yolks with no starch at all. It thickens because the yolk protein coagulates, and there is nothing protecting that protein from setting into lumps — so it must be held below a boil and stirred, and the moment it goes past is the moment it scrambles.
Pastry cream inverts every part of that. The starch coats the protein and keeps it from linking up, so the cream tolerates a boil, and it needs one. Applying custard technique to a pastry cream produces the delayed failure above; applying pastry cream technique to a custard produces scrambled egg.
The two are given the same name in British English, which is a large part of why this goes wrong.
Related
Things that go wrong
Pastry cream is lumpy, runny or grainy
Every cause is about how the starch and the yolk were cooked, which is the preparation rather than the bake it fills.
Used on and in
The classical filling for a bun whose whole structure is a hollow waiting to be filled.
Filled late, and often over a thin chocolate seal, because the cream's water will soften a blind-baked case within hours.
Baked in place, which is why a Danish cream is made stiffer than one used cold.
What it is built from
The starch that both thickens the cream and protects the yolk protein from setting into lumps, which is what lets it be boiled.
Richness and some set — and the starch-digesting enzyme that makes boiling non-negotiable.
The liquid the starch gelatinises into. Its water is what makes the cream perishable and what stops it freezing.
The science behind it
The thickening, and the reason the cream looks finished well before it has been heated enough.
What produces lumps when the yolks meet the hot milk too fast, and part of the set when they do not.
Keep reading
Buttercream
Sets by solid fat rather than by gelatinised starch, which is why the same complaint means something different in each.
Pastry cream is lumpy, runny or grainy
Work through what you can actually observe, rather than a list of possibilities.
Fillings, icings and creams
The whole family, grouped by what sets each one.