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Onion Soup

A thickened onion soup made with water, butter, minced Spanish onion, cornflour, and milk.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 5 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

Simmer the onion

  1. Boil the water and butter in a pot.

  2. Add the minced onion and boil for 1½ hours.

Thicken and serve

  1. Cool slightly, then mix the cornflour with the milk.

  2. Stir the cornflour mixture into the pot until it reaches boiling point.

  3. Season to taste and serve.

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

    Shared aroma: decanal (soap, orange peel).

  3. Onion + milktop 20% of all pairs
    Smell alikemoderate
    Cooked together13,418 recipes

    Shared aroma: hexanal (green, grassy).

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

What each ingredient does

Spanish onion
Cooks down over a long simmer to give the soup its main flavour and sweetness.
Cornflour
Swells with heat in the liquid, thickening the soup as it reaches boiling.
Milk
Adds body and richness, softening the flavour of the broth.
Butter
Adds fat that carries flavour and gives the soup a smoother mouthfeel.

The step that matters

Stirring in the cornflour mixture. Cornflour must be mixed smoothly with the milk first, then the soup must reach a full boil. Starch granules only swell and thicken fully at boiling point, and adding it unevenly can leave lumps.

Swap the onion

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

  1. Potatofits better
  2. Asparagusfits about as well
  3. Leekfits about as well
  4. Onionthe original

Fit is the average pairing score against butter, milk. 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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