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Onion Soup

A simple soup made with onions, butter, flour or oatmeal, water, pepper, salt, served over bread slices.

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 ↓

Onion Soup

Ingredients

Directions

Make the soup

  1. In a large saucepan, melt the butter over medium heat.

  2. Add the chopped onions and cook until they are light brown.

  3. Stir in the flour or oatmeal and mix well.

  4. Pour in the water and season with pepper and salt.

  5. Bring to a boil and stir for 20 minutes.

Serve

  1. Serve the soup over slices of bread in bowls.

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

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

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

    Shared aroma: isobutyraldehyde (malty, green).

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

    Shared aroma: decanal (soap, orange peel).

  5. Onion + breadtop 15% of all pairs
    Smell alikemoderate
    Cooked together8,676 recipes

    Shared aroma: 2,4-decadienal (seaweed).

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
Cooking until light brown builds sweet, savoury flavour that gives the soup its colour and depth.
Butter
Melts to cook the onions gently and adds richness to the soup.
Flour or oatmeal
Stirred in to thicken the soup as it simmers in the water.

The step that matters

Cooking the onions until light brown. Onions cooked too briefly stay sharp and pale, while longer cooking turns their natural sugars into browned, sweet flavour. Stirring keeps them from scorching.

Swap the onion

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

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

Fit is the average pairing score against butter, flour, 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.

More onion soup recipes

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

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