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Onion Soup

A creamy onion soup made with butter, onions, flour, milk, egg yolks, cream, salt, and pepper.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 8 ingredients
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Why it works: Butter and milk are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 81,283 recipes. Both carry (z)-4-heptenal, which smells biscuit, cream. The science ↓

Onion Soup

Ingredients

Directions

Make the soup

  1. Melt the butter in a large pot over medium heat until it bubbles.

  2. Add the sliced onions and simmer for 30 minutes without browning.

  3. Stir in the flour and cook until thickened.

  4. Gradually pour in the boiling milk while stirring.

  5. Season with salt and pepper, then press through a sieve back into the pot.

Finish and serve

  1. In a bowl, beat together the egg yolks and cream.

  2. Remove the soup from heat and quickly stir in the egg and cream mixture.

  3. Pour into a tureen and 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 + milktop 7% of all pairs
    Smell alikemoderate
    Cooked together81,283 recipes

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

  2. Butter + creamtop 8% of all pairs
    Smell alikemoderate
    Cooked together41,516 recipes

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

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

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

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

    Shared aroma: isobutyraldehyde (malty, green).

  5. Flour + milktop 14% of all pairs
    Smell alikelow
    Cooked together78,219 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

Onions
Soften and sweeten as they simmer, forming the body of the soup.
Flour
Thickens the milk into a smooth, lightly bodied soup.
Milk
Forms the liquid base that the onions and flour are cooked into.
Egg yolks
Enrich and thicken the soup for a silky, creamy texture.
Cream
Adds richness and smoothness to the finished soup.

The step that matters

Stirring in the egg and cream mixture. Egg yolks scramble if they get too hot. Removing the soup from heat before adding them and stirring quickly keeps the mixture smooth and thickened rather than curdled.

Swap the onion

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

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

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

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