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Eel Soup

A soup made from freshwater eels simmered with water, pepper, onion, sweet herbs, soy sauce, ketchup, and fried onions, served over toasted bread.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 10 ingredients
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Why it works: Sauce and ketchup match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 1,099 recipes. Both carry ethanol, which smells alcoholic, ethereal. The science ↓

Eel Soup

Ingredients

Directions

Make the soup

  1. In a pot, combine the eels, water, whole pepper, onion, and sweet herbs.

  2. Add soy sauce and ketchup, then simmer gently until the liquid reduces by half.

  3. Fry the onions in butter until browned, then add them and the butter to the soup.

Serve

  1. Strain the soup into a tureen over the pieces of toasted bread.

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. Sauce + ketchuptop 1% of all pairs
    Smell alikestrong
    Cooked together1,099 recipes

    Shared aroma: ethanol (alcoholic, ethereal).

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

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

  3. Pepper + oniontop 11% of all pairs
    Smell alikemoderate
    Cooked together68,474 recipes

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

  4. Sauce + buttertop 15% of all pairs
    Smell alikelow
    Cooked together15,338 recipes

    Shared aroma: ethanol (alcoholic, ethereal).

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

    Shared aroma: decanal (soap, orange peel).

Sauce and butter barely smell alike, yet cooks put them together in 15,338 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

Fresh-water eels
Provide the main protein and rich flavor that gives the soup its body.
Onions
Frying until browned adds sweetness and savory depth to the broth.
Butter
Carries the browning of the onions and adds richness to the finished soup.
Soy sauce
Adds savory, salty depth and deepens the color of the broth.
Ketchup
Adds sweetness and acidity that balance the savory broth.
Toasted bread
Soaks up broth and adds a dry, toasted texture to the soup.

The step that matters

Simmering until the liquid reduces by half. Simmering gently concentrates flavor and extracts gelatin from the eels. Boiling hard can make the broth cloudy and greasy, and stopping too early leaves it thin.

Swap the onion

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

  1. Capsicumfits better
  2. Shallotfits better
  3. Tomatofits better
  4. Onionthe original

Fit is the average pairing score against pepper, sauce, ketchup, butter, 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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