Honeycomb Toffee

This syrup reaches about 150 °C and it sticks to skin. Long sleeves, no children at the pan, and never taste or touch the mixture until it is cold and hard.

Line it before you turn on the heat. Deep, not wide — the mixture triples in volume and a shallow tray will overflow.

Measure 2 teaspoons of bicarbonate of soda into a small dish now. There is no time to fetch it later — the window is a few seconds wide.

Use 200 g caster sugar to 5 tablespoons of golden syrup in a pan at least three times the volume of the mixture.

Let the sugar dissolve gently, swirling the pan if you must. Stirring throws sugar crystals up the side and they seed the whole batch into grain.

Once fully dissolved, raise the heat. Keep the thermometer bulb in the syrup and clear of the pan base, which reads far hotter than the liquid.

Take it to 149-154 °C. Below that the foam collapses and you get chewy toffee; above it the sugar burns bitter. There is very little margin.

At temperature it should be a deep golden amber. If it is going brown at the edges, it is catching — pull it off immediately.

Remove it from the hob before adding anything. The reaction is violent and you do not want a flame under an overflowing pan.

Add it in one go and beat for about 3 seconds. The mixture erupts into pale foam and climbs the pan — this is the entire point of the recipe.

Every extra stroke knocks bubbles out. The difference between airy honeycomb and dense toffee is about two seconds of over-mixing.

Tip it straight in and leave it. Do not level it, do not spread it — smoothing the top compresses the foam you just made.

Do not put it in the fridge. Condensation makes the surface sticky and the structure slowly softens.

Smash it into shards. Sugar foam is hygroscopic and will pull moisture out of the air within hours, turning crisp cells into a sticky slab.

The reaction, precisely. Sodium bicarbonate decomposes on heating: 2 NaHCO₃ → Na₂CO₃ + H₂O + CO₂. It begins around 80 °C and runs to completion very fast at 150 °C, so all the gas is released essentially at once. Both the carbon dioxide and the steam from the water expand into the syrup. The sodium carbonate left behind is what gives honeycomb its faint soapy, alkaline edge — too much bicarb and that flavour dominates, which is why the quantity is not a matter of taste.

Why the bubbles stay. At 150 °C a sugar syrup contains only a few per cent water and is enormously viscous. Bubbles nucleate but cannot rise and escape before the mass cools through its glass transition and stops flowing altogether. Sugar at this concentration does not crystallise on cooling; it forms an amorphous glass, which is why honeycomb is transparent at the edges and fractures like glass rather than crumbling. Get the temperature 10 degrees lower and enough water remains that the syrup stays fluid, the bubbles escape, and you have made ordinary toffee by accident.

Why golden syrup is in the recipe. Golden syrup is largely invert sugar — glucose and fructose from partially hydrolysed sucrose. Mixing sugars interferes with crystal packing, so the melt is far less likely to seize into a grainy mass. Corn syrup or honey do the same job. This is the standard confectioner's trick for any glassy sugar work, from spun sugar to boiled sweets.

Four names, one sweet. It is cinder toffee or honeycomb in Britain, hokey pokey in New Zealand — where it is folded into ice cream as a national fixture — sponge candy around Buffalo and southern Ontario, and sea-foam or fairy food in parts of the American Midwest. The Crunchie bar, launched by Fry's in 1929, is a chocolate-coated version and is the form most people meet first. The name honeycomb is purely descriptive of the open cell structure; recipes that add honey are making something else.