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Lentil Soup

A simple lentil soup made by soaking, cooking, and seasoning lentils with butter, onion, flour, and salt.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 5 ingredients
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Why it works: Lentils and flour match in chemistry and in kitchens. They rank in the top 5% of all ingredient pairs, and cooks put them together in 255 recipes. Both carry isobutyraldehyde, which smells malty, green. The science ↓

Lentil Soup

Ingredients

Directions

Prepare the lentils

  1. Soak the lentils overnight in rainwater.

  2. The next morning, cook the lentils in the soaking water over moderate heat until thoroughly done.

  3. Add cold rainwater as needed during cooking.

  4. Pass the cooked lentils through a fine sieve.

Finish the soup

  1. In a separate pan, brown the flour and chopped onion in the butter.

  2. Stir the mixture into the soup and season with salt to taste.

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. Lentils + flourtop 5% of all pairs
    Smell alikestrong
    Cooked together255 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  2. Lentils + oniontop 8% of all pairs
    Smell alikestrong
    Cooked together1,221 recipes

    Shared aroma: coumarin (sweet, hay).

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

    Shared aroma: isobutyraldehyde (malty, green).

  4. Butter + oniontop 15% of all pairs
    Smell alikemoderate
    Cooked together42,912 recipes

    Shared aroma: decanal (soap, orange peel).

  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

Lentils
Form the body of the soup once cooked and sieved into a thick purée.
Butter
Carries flavour and adds richness to the browned base.
Onion
Browns in the butter to add savoury, sweet aroma to the soup.
Flour
Browns with the onion and thickens the soup slightly.

The step that matters

Browning the flour and onion in butter. Flour browns quickly and can turn bitter or burn if the heat is too high or it is left unattended. Stirring steadily gives an even, nutty colour and a smooth base that won't leave lumps when stirred into the soup.

Swap the onion

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

  1. Kalefits better
  2. Arrowrootfits better
  3. Shallotfits better
  4. Onionthe original

Fit is the average pairing score against lentils, butter, flour. 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 lentil soup recipes

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