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Onion Soup

A simple soup made with onion, potato, butter, milk, water, and herbs.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 8 ingredients
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Why it works: Onion and potato are a kitchen classic. They rank in the top 3% of all ingredient pairs, and cooks put them together in 9,023 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Onion Soup

Ingredients

Directions

Prepare

  1. Chop the onion and potato.

Make the soup

  1. In a saucepan, cook the vegetables in 2 cups of water with a pinch of herbs until tender.

  2. Rub the vegetables through a sieve back into the saucepan.

  3. Add the butter, milk, and season with pepper and salt.

  4. Heat gently 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. Onion + potatotop 3% of all pairs
    Smell alikemoderate
    Cooked together9,023 recipes

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

  2. Butter + milktop 7% of all pairs
    Smell alikemoderate
    Cooked together81,283 recipes

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

  3. Potato + peppertop 9% of all pairs
    Smell alikemoderate
    Cooked together8,305 recipes

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

  4. Potato + milktop 9% of all pairs
    Smell alikemoderate
    Cooked together3,611 recipes

    Shared aroma: (e,z)-2,6-nonadienal (cucumber, melon).

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

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

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

What each ingredient does

Spanish onion
Provides the sweet, savory base flavor of the soup.
Potato
Breaks down during cooking and sieving to give the soup body and a smooth texture.
Butter
Adds fat for richness and a silky mouthfeel.
Milk
Adds creaminess and mildness, softening the soup's flavor.

The step that matters

Rub the vegetables through a sieve. The vegetables must be cooked until fully tender so they pass easily through the sieve. Pushing them through breaks the cell walls and releases starch, which thickens the soup and gives it a smooth texture.

Swap the onion

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

  1. Capsicumfits better
  2. Asparagusfits about as well
  3. Tomatofits about as well
  4. Onionthe original

Fit is the average pairing score against potato, butter, pepper, 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.

More onion soup recipes

French 31Brown 15with Milk 7White 5Bavarian 4Bermuda 4 See all 236 →

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