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Bread

Onion Soup

A savory soup of onions, butter, water, bread crust, and French roll, seasoned with pepper and sea salt.

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

Make the soup

  1. Brown the butter with a little flour in a saucepan, being careful not to burn it.

  2. Slice the onions.

  3. Fry the sliced onions gently until tender.

  4. Gradually pour in the boiling water while shaking the pan.

  5. Add the crust of bread.

  6. Let the soup boil gently for 30 minutes.

  7. Season with pepper and salt.

  8. Let the soup boil for a while after the onions are tender to enhance the richness.

  9. Strain the soup.

Serve

  1. Dry the top of the French roll by the fire.

  2. Soak the French roll in some soup.

  3. Place the soaked roll in a tureen.

  4. Pour the strained soup over the French roll.

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. Onion + peppertop 11% of all pairs
    Smell alikemoderate
    Cooked together68,474 recipes

    Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).

  3. Butter + oniontop 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. Bread + peppertop 16% of all pairs
    Smell alikemoderate
    Cooked together20,964 recipes

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

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

What each ingredient does

Butter
Browns with flour to add a rich, nutty flavour and body to the soup.
White onions
Soften during frying and provide the sweetness and bulk of the soup.
Boiling water
Forms the liquid base of the soup that the onions and bread flavour.
Bread crust
Adds body and helps thicken the soup as it boils.
French roll
Soaks up the soup to become a moist, tender base in the tureen.

The step that matters

Browning the butter with flour. Butter can burn quickly, and burnt milk solids give a bitter taste that spoils the soup. Gentle heat and constant attention brown the butter and flour evenly for a nutty, deep colour and flavour.

Swap the onion

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

  1. Capsicumfits better
  2. Tomatofits better
  3. Potatofits about as well
  4. Onionthe original

Fit is the average pairing score against butter, bread, pepper. 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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French 31Brown 15with Milk 7White 5Bavarian 4Bermuda 4 See all 236 →

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