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Dessert

Lemon Filling

A lemon custard filling made with lemon juice, rind, sugar, egg, flour, and water, cooked until thickened.

From an old cookbook · modernised transcription
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Why it works: Sugar and flour are a kitchen classic. They rank in the top 15% of all ingredient pairs, and cooks put them together in 92,116 recipes. Both carry phenylacetaldehyde, which smells hawthorne, honey. The science ↓

Lemon Filling

Ingredients

Directions

  1. In a bowl, combine the lemon juice, grated rind, sugar, egg, flour, and water.

  2. Cook the mixture over simmering water until thickened.

  3. Allow to cool before spreading between cakes.

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 + flourtop 15% of all pairs
    Smell alikemoderate
    Cooked together92,116 recipes

    Shared aroma: phenylacetaldehyde (hawthorne, honey).

  2. Egg + flourtop 15% of all pairs
    Smell alikelow
    Cooked together106,462 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  3. Lemon + flourtop 17% of all pairs
    Smell alikemoderate
    Cooked together30,404 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  4. Lemon + sugartop 18% of all pairs
    Smell alikelow
    Cooked together53,532 recipes

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

  5. Lemon + eggtop 19% of all pairs
    Smell alikelow
    Cooked together44,316 recipes

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

Egg and flour barely smell alike, yet cooks put them together in 106,462 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

Egg
Thickens the filling as it cooks and gives it a rich, set body.
Sugar
Sweetens the filling and balances the sharpness of the lemon.
Lemon juice
Adds sharp acidity and bright lemon flavour.
Flour
Helps stabilise and thicken the filling so it holds its texture.

The step that matters

Cook over simmering water until thickened. Egg proteins set with gentle heat, so cooking slowly over simmering water thickens the filling without scrambling the egg. Too much heat can curdle it, while too little leaves it runny.

Swap the lemon

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

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

Fit is the average pairing score against sugar, egg, flour. 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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