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Onion Soup

A savory soup made with sliced onions, butter, flour, veal stock, and salt.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 5 ingredients
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Why it works: Butter and flour are a kitchen classic. They rank in the top 12% of all ingredient pairs, and cooks put them together in 124,287 recipes. Both carry isobutyraldehyde, which smells malty, green. The science ↓

Onion Soup

Ingredients

Directions

Prepare

  1. Slice the onions very thinly.

Make the soup

  1. In a pot, melt the butter and add the flour; cook until tender.

  2. Add the veal stock and bring to a boil for 20 minutes.

  3. Skim off any foam, then season with salt.

  4. Whisk to combine, reduce heat, and let it simmer 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 + flourtop 12% of all pairs
    Smell alikelow
    Cooked together124,287 recipes

    Shared aroma: isobutyraldehyde (malty, green).

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

    Shared aroma: decanal (soap, orange peel).

  3. Onion + vealtop 17% of all pairs
    Smell alikelow
    Cooked together6,841 recipes

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

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

    Shared aroma: isobutyraldehyde (malty, green).

  5. Butter + vealtop 23% of all pairs
    Smell alikemoderate
    Cooked together9,381 recipes

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

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
Supply the main flavour and the soft, textured body of the soup.
Butter
Adds fat and richness, carrying flavour into the soup.
Flour
Cooked with the butter to form a roux that thickens the stock.
Veal stock
Forms the liquid base that carries the soup's savoury flavour.

The step that matters

Cook the flour in the butter until tender. Cooking the flour in the melted butter before adding stock removes its raw, floury taste and coats the starch grains. This lets the flour thicken the liquid smoothly instead of forming lumps.

Swap the onion

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

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

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