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Onion Soup

A soup made from sliced onions, butter, water, salt, pepper, served with toasted bread and 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

The book gives no cooking times; the times in the steps were added in transcription, so check for doneness rather than trusting the clock.

Prepare

  1. Slice the onions thinly.

  2. In a pot, melt the butter over medium heat.

  3. Add the onions and cook until they are soft and golden.

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

  5. Simmer for 30 minutes.

Serve

  1. Serve hot with toasted bread and cheese on top.

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
Cooked slowly until soft and golden, they provide the main sweetness and body of the soup.
Butter
Melted into the pot to carry the onions' flavour and help them brown gently.
Bread
Toasted bread is served with the soup to add a crisp, contrasting texture.
Cheese
Placed on top of the soup, where it melts and adds richness and savoury flavour.

The step that matters

Cooking the onions until soft and golden. Cooking onions slowly in fat lets their natural sugars caramelise and build browning, which gives the soup its depth. Rushing this over high heat can scorch them, leaving bitter flavour instead of sweetness.

Swap the onion

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

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

Fit is the average pairing score against butter, pepper, 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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