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Onion Soup

A creamy onion soup made with butter, flour, and white broth, served over toasted bread topped with Swiss cheese.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 8 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 saucepan, brown the chopped onions in butter over medium heat.

  2. Stir in the flour, being careful not to burn it.

  3. Slowly add the white broth, mixing thoroughly until smooth.

  4. Season with salt and pepper, and cook for 10 minutes.

Assemble and bake

  1. Place the toasted bread in a large bowl and cover with thin slices of Swiss cheese.

  2. Pour the soup over the bread and cheese, then add the small pieces of Swiss cheese.

  3. Put in the oven for 5 minutes before serving.

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. Butter + swiss cheesetop 8% of all pairs
    Smell alikemoderate
    Cooked together413 recipes

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

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

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

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

    Shared aroma: isobutyraldehyde (malty, green).

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

    Shared aroma: decanal (soap, orange peel).

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
Browned in butter to build a sweet, deep flavour base for the soup.
Butter
Fat that browns the onions and carries their flavour into the soup.
Flour
Thickens the broth into a smooth, body-rich soup as it cooks.
White broth
Forms the liquid base of the soup.
Swiss cheese
Melts over the bread to add richness and a stretchy, browned topping.

The step that matters

Stirring in the flour. Flour left to burn turns bitter and dark, and it must be fully mixed in to avoid lumps. Cooking it briefly in the butter helps it thicken the broth smoothly.

Swap the onion

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

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

Fit is the average pairing score against butter, flour, pepper, bread, swiss 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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