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Leek Soup

A soup made from leeks, butter, stock, milk, flour, egg yolk, seasoned with pepper, salt, parsley, served with toast.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 10 ingredients
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Leek Soup

Why it works: Pepper and parsley match in chemistry and in kitchens. They rank in the top 2% of all ingredient pairs, and cooks put them together in 34,122 recipes. Both carry 4'-methylacetophenone, which smells bitter almond. The science ↓

Leek Soup

Ingredients

Directions

Prepare the leeks

  1. Cut off the green tops from the leeks and slice the rest.

  2. Fry the sliced leeks in butter until softened.

Make the soup

  1. Mix flour with hot milk, then add to the pot along with white stock.

  2. Season with pepper, salt, and parsley.

  3. Cook for 45 minutes, then stir in the egg yolk.

Serve

  1. Serve with small triangles of toast.

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.

Photo for illustrative purposes only · Contact us to use it

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. Pepper + parsleytop 2% of all pairs
    Smell alikestrong
    Cooked together34,122 recipes

    Shared aroma: 4'-methylacetophenone (bitter almond).

  2. Leek + parsleytop 4% of all pairs
    Smell alikestrong
    Cooked together759 recipes

    Shared aroma: trans-2-hexenal (green, leafy).

  3. Butter + milktop 7% of all pairs
    Smell alikemoderate
    Cooked together81,283 recipes

    Shared aroma: (z)-4-heptenal (biscuit, cream).

  4. Leek + flourtop 8% of all pairs
    Smell alikestrong
    Cooked together328 recipes

    Shared aroma: isobutyraldehyde (malty, green).

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

Leeks
Form the main body of the soup and give it their mild, sweet onion flavor.
Butter
Softens the leeks in fat and carries flavor into the soup.
Flour
Thickens the milk and stock, giving the soup a smooth, body-rich texture.
Egg yolk
Stirred in at the end to enrich and add richness and body to the soup.
Hot milk
Adds creaminess and mellows the soup's flavor.

The step that matters

Stir in the egg yolk after cooking. Egg yolk thickens through gentle heat, and if it boils it can curdle and turn grainy. Stirring it in off the boil, or with the heat low, keeps the soup smooth and silky.

Swap the leek

How well each one fits the dish's main ingredients (butter, milk, flour, pepper, parsley, egg):

  1. Shallotfits about as well
  2. Chivefits about as well
  3. Potatofits about as well
  4. Leekthe original

Fit is the average pairing score against butter, milk, flour, pepper, parsley, egg. 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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