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Onion Soup

A savory soup made with onions, butter, salt, cayenne, stock, egg yolks, bread, and cheese.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 8 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. Stir onions in butter over low heat for 1 hour, stirring frequently to avoid browning.

  2. Add salt, cayenne, and soup stock, then cook for an additional hour.

Assemble and serve

  1. Place the dried bread and grated cheese in a tureen.

  2. Beat the egg yolks with a ladle full of soup.

  3. Pour the egg mixture over the bread and cheese, covering it tightly for 5 minutes.

  4. Add the remaining soup to the tureen.

  5. Serve immediately.

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. Bread + cheesetop 7% of all pairs
    Smell alikemoderate
    Cooked together2,130 recipes

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

  3. Butter + cheesetop 8% of all pairs
    Smell alikemoderate
    Cooked together7,962 recipes

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

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

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

  5. Egg + breadtop 13% of all pairs
    Smell alikemoderate
    Cooked together22,662 recipes

    Shared aroma: (e)-2-octenal (fatty, green).

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

What each ingredient does

Onions
Slow cooking in butter softens and sweetens them, building the soup's base flavour.
Butter
Carries the onions' flavour and gives the soup richness and a silky body.
Egg yolks
Thicken the soup into a creamy custard when gently combined with the hot liquid.
Bread
Dried slices soak up the egg mixture and soup, giving the dish body and texture.
Grated cheese
Melts into the soaked bread, adding savoury flavour and stringy richness.

The step that matters

Beat the egg yolks with a ladle full of soup. Adding hot soup to yolks gradually, rather than all at once, tempers them so they thicken smoothly instead of scrambling into curds.

Swap the onion

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

  1. Capsicumfits better
  2. Asparagusfits better
  3. Potatofits better
  4. Onionthe original

Fit is the average pairing score against butter, pepper, egg, bread, cheese. 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.

More onion soup recipes

French 31Brown 15with Milk 7White 5Bavarian 4Bermuda 4 See all 236 →

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