Napoleon cake

Napoleon is puff pastry, custard and a night in the fridge. It is a cake where crispness and softness compete. Two problems come up most: the pastry puffs into rubbery pillows or stays raw, and the custard is runny or lumpy.

What it is made of

Top to bottom:

Six pastry layers and five of custard. The custard (crème pâtissière) is milk, sugar, eggs, butter and cornflour. The pastry is the crisp frame.

An honest note: in a classic Napoleon the cream is often richer, a butter-enriched custard. This custard is lighter. The cake is less greasy, but it softens the pastry faster.

Order of work

Pastry (can be done ahead): roll the dough thin, prick it with a fork and bake at about 200 °C between two trays or under a weight; otherwise the wet layers puff up like pillows. The sign of readiness is an even golden colour with no pale patches. Cool completely and keep dry. Good store-bought puff pastry is fine.

Custard (the day before): bring milk and sugar to steaming. Whisk the yolks with the starch separately, pour in the hot milk in a thin stream and cook, stirring, until thick. Starch thickens fully only when the custard comes to a boil and bubbles for a few minutes; an under-cooked one thins out later. Stir in the butter and cool under film pressed against the surface so no skin forms. Never assemble with warm custard: it melts the butter in the pastry.

Assembly:

1. Trim the layers to a common shape. Spread custard in an even layer of about 3 to 5 mm.
2. Stack the layers and press lightly; puff pastry is brittle.
3. Crush the top layer and press the crumbs around the cake.

Resting: 6 to 12 hours in the fridge. The custard moistens the pastry and it turns soft. If you like crunch, assemble a few hours before serving, though the cake will then shatter when cut.

What can go wrong

• Runny custard. It was under-cooked, so the starch did not set.
• Lumps in the custard. The hot milk went into the yolks too fast and they scrambled. Strain through a sieve.
• Domed pastry. No weight during baking and no pricking.
• Soggy cake. The custard was warm.

The verdict

Napoleon stands on two things: flat dry layers and a thick, cold custard. A few hours of resting decides whether it is crisp or soft.