Why royal icing suits gingerbread so well

Gingerbread and royal icing have been partners for centuries, and for good reason. Royal icing dries to a hard, glossy shell, so it holds a crisp piped line on a biscuit that is already firm and flat. It takes gel colours beautifully, it has no flavour of its own to compete with the spice, and once dry it will sit happily in a tin for a fortnight. For a UK kitchen, it is also inexpensive: icing sugar, egg white and a squeeze of lemon is all you really need.

It is not, however, completely forgiving. Humidity in a November kitchen will slow drying and can leave a tacky surface, and icing that is too thin will spread past your outline into a puddle. Get two things right — the bake of the biscuit and the consistency of the icing — and the rest is simply steady hands and a little patience.

Start with a biscuit worth decorating

Decoration only ever looks as neat as the base beneath it. A biscuit that has spread in the oven or cooked unevenly will give you a wobbly outline no matter how carefully you pipe.

• Roll to an even thickness. Aim for about 5mm. Rolling guides or a rolling pin with rings make this far easier than eyeballing it.
• Chill the cut shapes. Fifteen to twenty minutes in the fridge before baking sets the butter, so the edges stay sharp.
• Bake until just firm. Around 170°C fan, until the edges darken a shade and the centre feels barely set. A slightly tender middle is better than a brittle one.
• Use a dough with dark treacle or muscovado. It gives a softer crumb, which resists snapping when a small hand grips a decorated biscuit.
• Cool completely, then air-dry. Leave the biscuits uncovered for a few hours, or overnight, so the surface is dry. Icing laid on a still-warm biscuit will sink and crack.

Making the royal icing

Lightly whisk one large egg white (about 30g) with a few drops of lemon juice, then beat in 250g of icing sugar a spoonful at a time. Beat for five to eight minutes until the mixture stands in stiff peaks and loses that gritty feel between your fingers. Alternatively, whisk 15g of pasteurised dried egg white into 60ml of water before adding the sugar. Cover with cling film pressed onto the surface; royal icing skins over very quickly.

This stiff mixture is your starting point. Split it into bowls and thin each one gradually with water — a few drops at a time — until it reaches the consistency you need.

• Piping consistency: like thick toothpaste. A spoonful dropped back into the bowl sinks in fifteen to twenty seconds. Use this for outlines, lettering and fine detail.
• Flooding consistency: like runny honey. The ribbon vanishes in six to ten seconds and the surface settles smooth. Use this for filling areas.
• Colour first. Add gel paste colour before the final thinning, as it loosens the icing slightly. Liquid colouring will wreck your consistency.

Piping clean outlines

Fit a piping bag with a 1.5mm plain nozzle, or snip the very tip off a disposable bag. Fill it no more than two-thirds full and twist the top closed. Hold the bag at about 45 degrees with the nozzle a couple of millimetres above the biscuit, and let the icing fall onto the surface rather than pressing the tip into it. Keep the pressure even and move at a steady pace; stopping and starting mid-line leaves a lump.

To finish a line cleanly, release your grip on the bag and pull away sideways, or stop just short of the corner and ease the icing into place with a cocktail stick. If your hand wobbles, brace your wrist against the edge of the worktop or a tin. Piped outlines are also your dam: let them form a skin for ten to fifteen minutes before flooding, so the wet icing cannot escape over the edge.

Flooding, wet-on-wet and marbling

Flood using a piping bag with a slightly wider tip, or a squeezy bottle. Zigzag the icing inside the outline, then spread it with a cocktail stick or a small palette knife held flat, nudging it into the corners. Give the tray a gentle tap on the worktop to level the surface and bring bubbles up.

• Work in blocks of colour. Flood one colour at a time and leave it an hour or two before starting a neighbouring colour, or they will bleed into one another.
• Wet-on-wet: flood a base, then immediately pipe dots, stripes or swirls in a second colour and drag a cocktail stick through to feather or marble.
• Build depth in layers. Dry a flooded base fully, then pipe outlines, snowflakes or borders on top for a crisp, professional look.
• Keep the palette tight. Two or three colours against the warm brown of the biscuit always reads better than six.

Drying, storing and fixing faults

Leave flooded biscuits uncovered at room temperature for twelve to twenty-four hours. Keep them away from radiators, kettles and steamy windows. Never speed things up in a low oven — the icing will crater and separate from the biscuit.

If the flood escaped its outline, it was too thin; thicken the next batch slightly. Craters and a chalky bloom usually mean over-thinning, draughts or damp air. Cracks on drying point to an over-beaten or over-thick icing. Bubbles can be pricked with a cocktail stick while the icing is still wet, and any small mistake can be scraped away with the tip of a knife once dry and repiped over the top.

Once fully dry, store in a single layer in an airtight tin with greaseproof paper between the biscuits. Stack them too early and you will smudge the work you were so careful over. Eaten within two weeks, they are at their best — and they make a fine gift wrapped in cellophane on the day of giving.