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.
Make the soup
Slice the onions and sauté them in butter until golden brown.
Add water and bring to a boil.
Season with coarse sea salt and black pepper.
Simmer for 30 minutes.
Serve
Serve hot with toasted bread and melted Gruyère cheese on top.
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.
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Butter + breadtop 7% of all pairsSmell alikemoderateCooked together27,232 recipes
Shared aroma: delta-decalactone (sweet, creamy).
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Butter + gruyere cheesetop 9% of all pairsSmell alikemoderateCooked together323 recipes
Shared aroma: gamma-decalactone (peach, creamy).
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Onion + peppertop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Onion + buttertop 15% of all pairsSmell alikemoderateCooked together42,912 recipes
Shared aroma: decanal (soap, orange peel).
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Bread + gruyere cheesetop 15% of all pairsSmell alikemoderateCooked together38 recipes
Shared aroma: ethyl caproate (fruity, apple peel).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Onions
- Sweetness and savory depth as they caramelise during browning.
- Butter
- Fat that carries flavour and helps onions brown richly.
- Bread
- Soaks up the broth and gives the soup body when served toasted.
- Gruyere cheese
- Melts into a rich, stretchy topping with a nutty flavour.
The step that matters
Sauté the onions until golden brown. Onions must brown slowly over moderate heat so their sugars caramelise, building the deep flavour the broth depends on. Pale or burnt onions give a flat or bitter soup.
Swap the onion
How well each one fits the dish's main ingredients (butter, pepper, bread, gruyere cheese):
- Potatofits better
- Capsicumfits better
- Tomatofits about as well
- Onionthe original
Fit is the average pairing score against butter, pepper, bread, gruyere 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.
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