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Dessert

Boiled Icing for Cakes

A boiled icing made from refined sugar, water, egg whites, lemon, and optional indigo.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 5 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 ↓

Boiled Icing for Cakes

Ingredients

Directions

Make the syrup

  1. Break the sugar into small lumps.

  2. Pour cold water over the sugar, just enough to dissolve.

  3. Mash the lumps with a wooden spoon.

  4. Boil without skimming until the syrup is the consistency of honey.

  5. Strain the boiled syrup immediately after removing it from the heat.

Make the icing

  1. Beat the egg whites to a stiff froth, using 3 egg whites for every pound of sugar.

  2. Gradually stir in the beaten egg whites and lemon juice or essence until smooth and light.

  3. Add a few drops of indigo through a muslin bag for a pearly white color.

  4. If the icing is too thin, place the bowl in boiling water. Stir until it thickens.

  5. If the icing is too thick, add more beaten egg white a little at a time. Continue adding until the desired consistency is reached.

  6. Apply the icing while it is warm.

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

Refined loaf sugar
Forms the sweet syrup that sets into the body of the icing.
Egg whites
Whipped to a foam that gives the icing its light, airy structure.
Lemon juice
Adds acidity that helps keep the icing smooth and balances the sweetness.

The step that matters

Boil without skimming until the syrup is the consistency of honey. Boiling sugar syrup to the right concentration controls how firm the icing becomes once cooled and mixed with the egg whites. Undercooked syrup gives a runny icing, while overcooked syrup turns hard and brittle.

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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