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Soup

White Onion Soup

A smooth soup of sliced onions cooked in butter, simmered with milk, white stock and bread crusts, then sieved.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 7 ingredients
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Why it works: Butter and bread are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 27,232 recipes. Both carry delta-decalactone, which smells sweet, creamy. The science ↓

White Onion Soup

Ingredients

Directions

Prepare the onions

  1. Peel and slice the onions.

  2. In a saucepan, melt the butter.

  3. Add the onions to the butter.

  4. Cook the onions over low heat, covered, for 1 hour without browning.

  5. Add the dry crusts of bread to the onions.

Simmer and strain

  1. Boil the milk and stock together.

  2. Pour the milk and stock over the onions and bread.

  3. Cover and simmer slowly for 1 hour.

  4. Rub the mixture through a sieve.

Season and serve

  1. Season with salt, pepper, and a few drops of lemon juice.

  2. Bring to a boil.

  3. Serve with fried bread.

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 + breadtop 7% of all pairs
    Smell alikemoderate
    Cooked together27,232 recipes

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

  2. Milk + buttertop 7% of all pairs
    Smell alikemoderate
    Cooked together81,283 recipes

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

  3. Milk + breadtop 11% of all pairs
    Smell alikemoderate
    Cooked together11,466 recipes

    Shared aroma: 2-undecenal (sweet).

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

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

  5. Butter + oniontop 15% of all pairs
    Smell alikemoderate
    Cooked together42,912 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

Onions
Provide the main flavour and body of the soup as they soften and sweeten.
Milk
Adds creaminess and a smooth, rich texture to the soup.
White bone stock
Supplies the liquid base and savoury depth for the soup.
Dry bread crusts
Absorb liquid and help thicken the soup when rubbed through a sieve.
Butter
Adds fat and richness while gently cooking the onions.

The step that matters

Cook the onions over low heat without browning. Gentle, covered cooking softens the onions and draws out their sweetness. Browning would add bitter, caramelized notes that change the soup's pale, delicate flavour.

Swap the onion

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

  1. Capsicumfits better
  2. Potatofits better
  3. Tomatofits better
  4. Onionthe original

Fit is the average pairing score against milk, butter, pepper, bread. 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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