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Leek Soup

A soup made from leeks, butter, stock, milk, flour, egg yolk, and seasonings, 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 and cook the leeks

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

  2. Fry the leeks in the butter until softened.

Make the soup

  1. Add the white stock and hot milk mixed with flour.

  2. Season with pepper, coarse sea 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 body of the soup, becoming soft and sweet as they cook.
Butter
Fat that softens the leeks and carries their flavour.
Flour
Thickens the stock and milk into a smooth, lightly body-rich soup.
Milk
Adds creaminess and mild sweetness to the soup.
Egg yolk
Enriches and thickens the soup when stirred in at the end.

The step that matters

Stir in the egg yolk. Egg yolk thickens when heated, but if the soup is boiling hot it can scramble into specks. Removing the pan from strong heat before stirring in the yolk keeps the soup 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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