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Brown Onion Soup

A soup made from browned onions, water, and seasonings, finished with egg yolks and vinegar.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 8 ingredients
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Why it works: Onion and pepper are a kitchen classic. They rank in the top 11% of all ingredient pairs, and cooks put them together in 68,474 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Brown Onion Soup

Ingredients

Directions

Prepare the onions

  1. Peel and cut the onions.

  2. Fry the onions in butter until browned and tender.

  3. Remove the onions and drain them on a sieve.

Make the soup

  1. Place the onions in a pot with boiling water and let them boil for 1 hour, stirring often.

  2. Add pepper and salt to taste.

  3. Rub the crumbs of the roll through a colander and add to the soup, stirring well to prevent lumps.

  4. Boil for an additional 2 hours.

Finish and serve

  1. Before serving, beat the egg yolks with vinegar and a little soup, adding gradually while stirring continuously.

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

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

  2. Onion + vinegartop 14% of all pairs
    Smell alikemoderate
    Cooked together18,226 recipes

    Shared aroma: acetic acid (sour, vinegar).

  3. Pepper + vinegartop 14% of all pairs
    Smell alikemoderate
    Cooked together27,814 recipes

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

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

    Shared aroma: decanal (soap, orange peel).

  5. Butter + eggtop 17% of all pairs
    Smell alikemoderate
    Cooked together118,967 recipes

    Shared aroma: decanal (soap, orange peel).

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

What each ingredient does

Spanish onions
Provide the main body and sweet, savoury flavour of the soup as they brown and soften.
Butter
Fat that browns the onions, adding richness and toasted flavour.
Roll crumbs
Starch that thickens the soup body and gives it a fuller texture.
Egg yolks
Enrich the soup and thicken it slightly when gently blended in at the end.
Vinegar
Adds a sharp acidity that brightens the rich, sweet onion flavour.

The step that matters

Adding the egg yolk mixture. Egg yolks can scramble and curdle if they meet very hot liquid too quickly. Beating them with vinegar and a little soup first, then adding gradually while stirring, tempers them so the soup becomes smooth and lightly thickened.

Swap the onion

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

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

Fit is the average pairing score against butter, pepper, egg, vinegar. 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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