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Dessert

Boiled Icing

A clear, stiff icing made by boiling powdered sugar and water, then folding into beaten egg whites.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 5 ingredients
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Why it works: Sugar and vanilla are a kitchen classic. They rank in the top 8% of all ingredient pairs, and cooks put them together in 35,032 recipes. Both carry beta-damascenone, which smells apple, rose. The science ↓

Boiled Icing

Ingredients

Directions

Make the syrup

  1. Combine powdered sugar and water in a saucepan.

  2. Let the mixture stand until dissolved.

  3. Boil the mixture until it is perfectly clear.

Make the icing

  1. Beat the egg whites in a separate bowl until stiff.

  2. Once the sugar syrup is lukewarm, pour it over the egg whites while beating continuously.

  3. Add citric acid and vanilla extract to taste.

  4. Continue beating for one hour.

Ice and dry the cake

  1. Rub the cake with a little flour before applying the icing.

  2. Spread the icing on the cake with a wet knife.

  3. Wet the knife in cold water as needed.

  4. Set the cake in a warm place to dry.

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 + vanillatop 8% of all pairs
    Smell alikelow
    Cooked together35,032 recipes

    Shared aroma: beta-damascenone (apple, rose).

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

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

  3. Egg + vanillatop 23% of all pairs
    Smell alikelow
    Cooked together27,347 recipes

    Shared aroma: 1-octen-3-ol (mushroom, earthy).

Sugar and vanilla barely smell alike, yet cooks put them together in 35,032 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

Powdered sugar
Dissolves into the syrup that gives the icing its sweetness and body.
Egg whites
Whipped to stiff foam, they give the icing its light, airy structure.
Citric acid
Adds a touch of acidity that balances sweetness and helps keep the icing stable.

The step that matters

Boil the syrup until perfectly clear. Boiling the sugar and water to a clear syrup dissolves the sugar fully and drives off enough water. Under-boiled syrup can leave the icing thin or grainy, while overcooked syrup can make it stiff and hard to spread.

“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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