Peanut Brittle Day

What the day is

Peanut Brittle Day is observed on January 26. Brittle is sugar cooked hard with nuts through it, and it has one ingredient that does something genuinely clever.

Origin and background

Cooked to the hard crack stage, sugar sets into an amorphous glass, and a solid sheet of it is unpleasant to eat: it does not break so much as resist, and then break somewhere you did not want. Good brittle is thin, light and shatters cleanly, and the reason is the baking soda stirred in at the very end.

Baking soda in contact with hot syrup, particularly syrup containing acid, releases carbon dioxide. Added at the last moment the mixture foams up dramatically, and because the sugar is already near setting point those bubbles are locked in place as it cools. The finished brittle is therefore full of tiny voids, which is what makes it porous, lighter in color, and able to fracture cleanly instead of behaving like a windowpane. Honeycomb and cinder toffee are the same trick taken further.

The other variable is when the nuts go in. Added early they cook in the syrup and toast through, which deepens the flavor but risks burning. Added late they stay raw-tasting. Most recipes split the difference by adding raw peanuts partway through the cook so they toast in the sugar itself.

Like all boiled sugar, brittle is ruined by humidity, pulling moisture from the air until the surface goes tacky. Airtight storage the moment it cools is not optional.

Two safety notes worth stating: sugar at this temperature causes serious burns and sticks to skin, and the soda stage foams up fast, so the pan needs far more headroom than seems necessary.

How to take part

• Use a thermometer and a pan much larger than you think you need.
• Have the baking soda measured and to hand before you start. There is no time to fetch it.
• Stir it in fast and pour immediately, before the foam settles.
• Spread it thin and let it set undisturbed.
• Store it airtight straight away, and keep children clear of the pan.