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Dessert

Royal Icing

A sweet glaze made from icing sugar, lemon juice, and egg whites.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 3 ingredients
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Why it works: Sugar and lemon are a kitchen classic. They rank in the top 18% of all ingredient pairs, and cooks put them together in 53,532 recipes. Both carry 2-nonenal, which smells fatty, green. The science ↓

Royal Icing

Oven, in the book's wordsA cool oven

Ingredients

Directions

Make the icing

  1. Sift the icing sugar to remove lumps.

  2. In a bowl, combine the icing sugar, lemon juice, and slightly beaten egg whites.

  3. Beat well with a wooden spoon until very white and smooth.

Ice the cake

  1. Ensure the cake top is level.

  2. If needed, trim the top and brush with egg white.

  3. Spread the icing on top of the cake, then use a cold, wet knife to smooth it down the sides.

  4. Place the cake in a cool oven for a few minutes to set the egg.

  5. Let the cake sit in a cool oven until the icing sets, ideally overnight before decorating.

  6. For decorating cakes, transfer the icing to a piping bag with a fancy tip.

Recipe from a historical cookbook (Internet Archive).

Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.

Explore the science

The flavor team

The pairs that carry this dish. Each one is judged two ways: how much their aromas overlap, and how often cooks already put them together.

  1. Sugar + lemontop 18% of all pairs
    Smell alikelow
    Cooked together53,532 recipes

    Shared aroma: 2-nonenal (fatty, green).

  2. Egg + lemontop 19% of all pairs
    Smell alikelow
    Cooked together44,316 recipes

    Shared aroma: (e,e)-2,4-decadienal (fatty, deep fried).

  3. Sugar + eggtop 21% of all pairs
    Smell alikemoderate
    Cooked together122,807 recipes

    Shared aroma: 2-nonenal (fatty, green).

Sugar and lemon barely smell alike, yet cooks put them together in 53,532 recipes: they work on texture and structure more than aroma.

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

What each ingredient does

Icing sugar
Forms the bulk of the icing and gives it sweetness and body as it dries.
Egg whites
Provide structure and help the icing dry to a hard, smooth finish.
Lemon juice
Adds acidity that brightens the flavour and helps keep the icing white.

The step that matters

Beat until very white and smooth. Thorough beating incorporates air and dissolves the sugar evenly, so the icing spreads smoothly and sets with a glossy, firm surface instead of a grainy or soft one.

Swap the lemon

How well each one fits the dish's main ingredients (sugar, egg):

  1. Vanillafits better
  2. Raisinfits about as well
  3. Lemonthe original
  4. Datesfits less well

Fit is the average pairing score against sugar, egg. Candidates are from the same food group and used in at least 100 recipes.

“What each ingredient does” and “The step that matters” were written by Claude from this recipe’s own method and reviewed in samples by CompKitchen.

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