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Onion Soup

A savory soup made with onions, butter, flour, broth, salt, peppercorns, and bread.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 7 ingredients
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Why it works: Butter and bread are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 27,232 recipes. Both carry delta-decalactone, which smells sweet, creamy. The science ↓

Onion Soup

Ingredients

Directions

Prepare

  1. Cut the onions into shreds.

Make the soup

  1. Brown the onions in a stew-pan with butter until tender and browned.

  2. Add flour and cook until it takes on a nice color.

  3. Gradually dilute with boiling broth, season with salt and peppercorns, and bring to a boil.

  4. Add bread and simmer for a while before serving.

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 + breadtop 7% of all pairs
    Smell alikemoderate
    Cooked together27,232 recipes

    Shared aroma: delta-decalactone (sweet, creamy).

  2. Butter + flourtop 12% of all pairs
    Smell alikelow
    Cooked together124,287 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  3. Onion + buttertop 15% of all pairs
    Smell alikemoderate
    Cooked together42,912 recipes

    Shared aroma: decanal (soap, orange peel).

  4. Onion + breadtop 15% of all pairs
    Smell alikemoderate
    Cooked together8,676 recipes

    Shared aroma: 2,4-decadienal (seaweed).

  5. Onion + flourtop 17% of all pairs
    Smell alikemoderate
    Cooked together32,460 recipes

    Shared aroma: isobutyraldehyde (malty, green).

Butter and flour barely smell alike, yet cooks put them together in 124,287 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

Onions
Browning in butter builds the sweet, deep flavor that defines the soup.
Butter
Fat that carries the onions' browning and adds richness.
Flour
Cooked with the fat, it thickens the broth into a smoother body.
Broth
Liquid base that becomes the body of the soup.
Bread
Soaks up broth during simmering, giving the soup body and a soft texture.

The step that matters

Adding the broth gradually. Pouring the boiling broth in slowly while stirring lets the flour disperse evenly, which prevents lumps and keeps the soup smooth.

Swap the onion

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

  1. Shallotfits better
  2. Leekfits better
  3. Chivefits better
  4. Onionthe original

Fit is the average pairing score against butter, flour, bread. 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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