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Dessert

Foaming Sauce

A sweet lemon sauce made with powdered sugar, butter, eggs, and boiling water, finished with nuts or fruit.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 8 ingredients
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Why it works: Butter and lemon are a kitchen classic. They rank in the top 16% of all ingredient pairs, and cooks put them together in 41,227 recipes. Both carry 3-hexenal, which smells apple, fruity. The science ↓

Foaming Sauce

Ingredients

Directions

Make the sauce

  1. Mix powdered sugar and butter together.

  2. Add egg yolks, lemon rind, and lemon juice.

  3. Beat egg whites until stiff and fold into the mixture.

Serve

  1. Just before serving, quickly stir in boiling water.

  2. Add chopped nuts or crushed fruit as desired.

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. Butter + lemontop 16% of all pairs
    Smell alikemoderate
    Cooked together41,227 recipes

    Shared aroma: 3-hexenal (apple, fruity).

  2. Butter + eggtop 17% of all pairs
    Smell alikemoderate
    Cooked together118,967 recipes

    Shared aroma: decanal (soap, orange peel).

  3. Sugar + buttertop 17% of all pairs
    Smell alikemoderate
    Cooked together98,233 recipes

    Shared aroma: guaiacol (smoky, sweet).

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

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

  5. Butter + nutstop 19% of all pairs
    Smell alikemoderate
    Cooked together1,291 recipes

    Shared aroma: 2,3-pentanedione (butter, sweet).

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

Butter
Adds richness and fat, giving the sauce a smooth, creamy body.
Egg whites
Whipped to stiff peaks, they trap air and give the sauce its light, foamy texture.
Egg yolks
Add richness and emulsify with the butter and sugar for a smooth base.
Powdered sugar
Sweetens the sauce and dissolves easily into the butter for a smooth base.
Lemon juice
Adds acidity that brightens the sweetness and balances the richness.

The step that matters

Just before serving, quickly stir in boiling water. Boiling water must be added at the last moment and stirred quickly. Adding it early or stirring slowly lets the foam collapse and the sauce lose its light, airy texture.

Swap the nuts

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

  1. Almondfits better
  2. Pistachiofits better
  3. Walnutfits better
  4. Nutsthe original

Fit is the average pairing score against sugar, butter, egg, lemon. 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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