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Onion Soup

A savory soup of sautéed onions in butter, simmered with water, seasoned with salt and pepper, served with toasted bread and melted cheese.

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. Slice the onions and sauté them in butter until golden brown.

  2. Add water and season with coarse sea salt and pepper.

  3. Simmer for 30 minutes.

Top and serve

  1. Toast the bread and place it on top of the soup.

  2. Sprinkle cheese on the bread and broil until melted.

  3. Serve hot.

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. Bread + cheesetop 7% of all pairs
    Smell alikemoderate
    Cooked together2,130 recipes

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

  3. Butter + cheesetop 8% of all pairs
    Smell alikemoderate
    Cooked together7,962 recipes

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

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

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

  5. Onion + buttertop 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
Break down slowly during browning to add deep, sweet flavour to the broth.
Butter
Carries heat to the onions and helps them brown to a golden colour.
Bread
Soaks up some broth and forms a base that holds the melted cheese.
Cheese
Melts and browns on top, adding richness and a savoury crust.

The step that matters

Sauté the onions until golden brown. Onions need steady, moderate heat to caramelise. Rushing over high heat scorches the sugars and makes a bitter taste, while stopping too early leaves the soup flat and pale.

Swap the onion

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

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

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